boomerang.js

/**
 * @copyright (c) 2011, Yahoo! Inc.  All rights reserved.
 * @copyright (c) 2012, Log-Normal, Inc.  All rights reserved.
 * @copyright (c) 2012-2017, SOASTA, Inc. All rights reserved.
 * @copyright (c) 2017-2023, Akamai Technologies, Inc. All rights reserved.
 * Copyrights licensed under the BSD License. See the accompanying LICENSE.txt file for terms.
 */

/**
 * @class BOOMR
 * @desc
 * boomerang measures various performance characteristics of your user's browsing
 * experience and beacons it back to your server.
 *
 * To use this you'll need a web site, lots of users and the ability to do
 * something with the data you collect.  How you collect the data is up to
 * you, but we have a few ideas.
 *
 * Everything in boomerang is accessed through the `BOOMR` object, which is
 * available on `window.BOOMR`.  It contains the public API, utility functions
 * ({@link BOOMR.utils}) and all of the plugins ({@link BOOMR.plugins}).
 *
 * Each plugin has its own API, but is reachable through {@link BOOMR.plugins}.
 *
 * ## Beacon Parameters
 *
 * The core boomerang object will add the following parameters to the beacon.
 *
 * Note that each individual {@link BOOMR.plugins plugin} will add its own
 * parameters as well.
 *
 * * `v`: Boomerang version
 * * `sv`: Boomerang Loader Snippet version
 * * `sm`: Boomerang Loader Snippet method
 * * `u`: The page's URL (for most beacons), or the `XMLHttpRequest` URL
 * * `n`: The beacon number
 * * `pgu`: The page's URL (for `XMLHttpRequest` beacons)
 * * `pid`: Page ID (8 characters)
 * * `r`: Navigation referrer (from `document.location`)
 * * `vis.pre`: `1` if the page transitioned from prerender to visible
 * * `vis.st`: Document's visibility state when beacon was sent
 * * `vis.lh`: Timestamp when page was last hidden
 * * `vis.lv`: Timestamp when page was last visible
 * * `xhr.pg`: The `XMLHttpRequest` page group
 * * `errors`: Error messages of errors detected in Boomerang code, separated by a newline
 * * `rt.si`: Session ID
 * * `rt.ss`: Session start timestamp
 * * `rt.sl`: Session length (number of pages), can be increased by XHR beacons as well
 * * `ua.plt`: `navigator.platform` or if available `navigator.userAgentData.platform`
 * * `ua.arch`: navigator userAgentData architecture, if client hints requested
 * * `ua.model`: navigator userAgentData model, if client hints requested
 * * `ua.pltv`: navigator userAgentData platform version, if client hints requested
 * * `ua.vnd`: `navigator.vendor`
 */

/**
 * @typedef TimeStamp
 * @type {number}
 *
 * @desc
 * A [Unix Epoch](https://en.wikipedia.org/wiki/Unix_time) timestamp (milliseconds
 * since 1970) created by [BOOMR.now()]{@link BOOMR.now}.
 *
 * If `DOMHighResTimeStamp` (`performance.now()`) is supported, it is
 * a `DOMHighResTimeStamp` (with microsecond resolution in the fractional),
 * otherwise, it is `Date.now()`.
 */

/* BEGIN_DEBUG */
// we don't yet have BOOMR.utils.mark()
if ("performance" in window &&
  window.performance &&
  typeof window.performance.mark === "function" &&
  !window.BOOMR_no_mark) {
  window.performance.mark("boomr:startup");
}
/* END_DEBUG */

/**
 * @global
 * @type {TimeStamp}
 * @desc
 * This variable is added to the global scope (`window`) until Boomerang loads,
 * at which point it is removed.
 *
 * Timestamp the boomerang.js script started executing.
 *
 * This has to be global so that we don't wait for this entire
 * script to download and execute before measuring the
 * time.  We also declare it without `var` so that we can later
 * `delete` it.  This is the only way that works on Internet Explorer.
 */
BOOMR_start = new Date().getTime();

/**
 * @function
 * @global
 * @desc
 * This function is added to the global scope (`window`).
 *
 * Check the value of `document.domain` and fix it if incorrect.
 *
 * This function is run at the top of boomerang, and then whenever
 * {@link BOOMR.init} is called.  If boomerang is running within an IFRAME, this
 * function checks to see if it can access elements in the parent
 * IFRAME.  If not, it will fudge around with `document.domain` until
 * it finds a value that works.
 *
 * This allows site owners to change the value of `document.domain` at
 * any point within their page's load process, and we will adapt to
 * it.
 *
 * @param {string} domain Domain name as retrieved from page URL
 */
function BOOMR_check_doc_domain(domain) {
  /* eslint no-unused-vars:0 */
  var test;

  /* BEGIN_DEBUG */
  // we don't yet have BOOMR.utils.mark()
  if ("performance" in window &&
    window.performance &&
    typeof window.performance.mark === "function" &&
    !window.BOOMR_no_mark) {
    window.performance.mark("boomr:check_doc_domain");
  }
  /* END_DEBUG */

  if (!window) {
    return;
  }

  // If domain is not passed in, then this is a global call
  // domain is only passed in if we call ourselves, so we
  // skip the frame check at that point
  if (!domain) {
    // If we're running in the main window, then we don't need this
    if (window.parent === window || !document.getElementById("boomr-if-as")) {
      // nothing to do
      return;
    }

    if (window.BOOMR && BOOMR.boomerang_frame && BOOMR.window) {
      try {
        // If document.domain is changed during page load (from www.blah.com to blah.com, for example),
        // BOOMR.window.location.href throws "Permission Denied" in IE.
        // Resetting the inner domain to match the outer makes location accessible once again
        if (BOOMR.boomerang_frame.document.domain !== BOOMR.window.document.domain) {
          BOOMR.boomerang_frame.document.domain = BOOMR.window.document.domain;
        }
      }
      catch (err) {
        if (!BOOMR.isCrossOriginError(err)) {
          BOOMR.addError(err, "BOOMR_check_doc_domain.domainFix");
        }
      }
    }

    domain = document.domain;
  }

  if (!domain || domain.indexOf(".") === -1) {
    // not okay, but we did our best
    return;
  }

  // window.parent might be null if we're running during unload from
  // a detached iframe
  if (!window.parent) {
    return;
  }

  // 1. Test without setting document.domain
  try {
    test = window.parent.document;

    // all okay
    return;
  }
  // 2. Test with document.domain
  catch (err) {
    try {
      document.domain = domain;
    }
    catch (err2) {
      // An exception might be thrown if the document is unloaded
      // or when the domain is incorrect.  If so, we can't do anything
      // more, so bail.
      return;
    }
  }

  try {
    test = window.parent.document;

    // all okay
    return;
  }
  // 3. Strip off leading part and try again
  catch (err) {
    domain = domain.replace(/^[\w\-]+\./, "");
  }

  BOOMR_check_doc_domain(domain);
}

BOOMR_check_doc_domain();

// Construct BOOMR
// w is window
(function(w) {
  var impl, boomr, d, createCustomEvent, dispatchEvent, visibilityState, visibilityChange,
      orig_w = w;

  // If the window that boomerang is running in is not top level (ie, we're running in an iframe)
  // and if this iframe contains a script node with an id of "boomr-if-as",
  // Then that indicates that we are using the iframe loader, so the page we're trying to measure
  // is w.parent
  //
  // Note that we use `document` rather than `w.document` because we're specifically interested in
  // the document of the currently executing context rather than a passed in proxy.
  //
  // The only other place we do this is in `BOOMR.utils.getMyURL` below, for the same reason, we
  // need the full URL of the currently executing (boomerang) script.
  if (w.parent !== w &&
      document.getElementById("boomr-if-as") &&
      document.getElementById("boomr-if-as").nodeName.toLowerCase() === "script") {
    w = w.parent;
  }

  d = w.document;

  // Short namespace because I don't want to keep typing BOOMERANG
  if (!w.BOOMR) {
    w.BOOMR = {};
  }

  BOOMR = w.BOOMR;

  // don't allow this code to be included twice
  if (BOOMR.version) {
    return;
  }

  /**
   * Boomerang version, formatted as major.minor.patchlevel.
   *
   * This variable is replaced during build (`grunt build`).
   *
   * @type {string}
   *
   * @memberof BOOMR
   */
  BOOMR.version = "%boomerang_version%";

  /**
   * The main document window.
   * * If Boomerang was loaded in an IFRAME, this is the parent window
   * * If Boomerang was loaded inline, this is the current window
   *
   * @type {Window}
   *
   * @memberof BOOMR
   */
  BOOMR.window = w;

  /**
   * The Boomerang frame:
   * * If Boomerang was loaded in an IFRAME, this is the IFRAME
   * * If Boomerang was loaded inline, this is the current window
   *
   * @type {Window}
   *
   * @memberof BOOMR
   */
  BOOMR.boomerang_frame = orig_w;

  /**
   * @class BOOMR.plugins
   * @desc
   * Boomerang plugin namespace.
   *
   * All plugins should add their plugin object to `BOOMR.plugins`.
   *
   * A plugin should have, at minimum, the following exported functions:
   * * `init(config)`
   * * `is_complete()`
   *
   * See {@tutorial creating-plugins} for details.
   */
  if (!BOOMR.plugins) {
    BOOMR.plugins = {};
  }

  // CustomEvent proxy for IE9 & 10 from https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent
  (function() {
    try {
      if (new w.CustomEvent("CustomEvent") !== undefined) {
        createCustomEvent = function(e_name, params) {
          return new w.CustomEvent(e_name, params);
        };
      }
    }
    catch (ignore) {
      // empty
    }

    try {
      if (!createCustomEvent && d.createEvent && d.createEvent("CustomEvent")) {
        createCustomEvent = function(e_name, params) {
          var evt = d.createEvent("CustomEvent");

          params = params || { cancelable: false, bubbles: false };
          evt.initCustomEvent(e_name, params.bubbles, params.cancelable, params.detail);

          return evt;
        };
      }
    }
    catch (ignore) {
      // empty
    }

    if (!createCustomEvent && d.createEventObject) {
      createCustomEvent = function(e_name, params) {
        var evt = d.createEventObject();

        evt.type = evt.propertyName = e_name;
        evt.detail = params.detail;

        return evt;
      };
    }

    if (!createCustomEvent) {
      createCustomEvent = function() {
        return undefined;
      };
    }
  }());

  /**
   * Dispatch a custom event to the browser
   * @param {string} e_name The custom event name that consumers can subscribe to
   * @param {object} e_data Any data passed to subscribers of the custom event via the `event.detail` property
   * @param {boolean} async By default, custom events are dispatched immediately.
   * Set to true if the event should be dispatched once the browser has finished its current
   * JavaScript execution.
   */
  dispatchEvent = function(e_name, e_data, async) {
    var ev = createCustomEvent(e_name, {"detail": e_data});

    if (!ev) {
      return;
    }

    function dispatch() {
      try {
        if (d.dispatchEvent) {
          d.dispatchEvent(ev);
        }
        else if (d.fireEvent) {
          d.fireEvent("onpropertychange", ev);
        }
      }
      catch (e) {
        BOOMR.debug("Error when dispatching " + e_name);
      }
    }

    if (async) {
      BOOMR.setImmediate(dispatch);
    }
    else {
      dispatch();
    }
  };

  // visibilitychange is useful to detect if the page loaded through prerender
  // or if the page never became visible
  // https://www.w3.org/TR/2011/WD-page-visibility-20110602/
  // https://www.nczonline.net/blog/2011/08/09/introduction-to-the-page-visibility-api/
  // https://developer.mozilla.org/en-US/docs/Web/Guide/User_experience/Using_the_Page_Visibility_API

  // Set the name of the hidden property and the change event for visibility
  if (typeof d.hidden !== "undefined") {
    visibilityState = "visibilityState";
    visibilityChange = "visibilitychange";
  }
  else if (typeof d.mozHidden !== "undefined") {
    visibilityState = "mozVisibilityState";
    visibilityChange = "mozvisibilitychange";
  }
  else if (typeof d.msHidden !== "undefined") {
    visibilityState = "msVisibilityState";
    visibilityChange = "msvisibilitychange";
  }
  else if (typeof d.webkitHidden !== "undefined") {
    visibilityState = "webkitVisibilityState";
    visibilityChange = "webkitvisibilitychange";
  }

  // impl is a private object not reachable from outside the BOOMR object.
  // Users can set properties by passing in to the init() method.
  impl = {
    // Beacon URL
    beacon_url: "",

    // Forces protocol-relative URLs to HTTPS
    beacon_url_force_https: true,

    // List of string regular expressions that must match the beacon_url.  If
    // not set, or the list is empty, all beacon URLs are allowed.
    beacon_urls_allowed: [],

    // Beacon request method, either GET, POST or AUTO. AUTO will check the
    // request size then use GET if the request URL is less than MAX_GET_LENGTH
    // chars. Otherwise, it will fall back to a POST request.
    beacon_type: "AUTO",

    // Beacon authorization key value. Most systems will use the 'Authentication'
    // keyword, but some some services use keys like 'X-Auth-Token' or other
    // custom keys.
    beacon_auth_key: "Authorization",

    // Beacon authorization token. This is only needed if your are using a POST
    // and the beacon requires an Authorization token to accept your data.  This
    // disables use of the browser sendBeacon() API.
    beacon_auth_token: undefined,

    // Sends beacons with Credentials (applies to XHR beacons, not IMG or `sendBeacon()`).
    // If you need this, you may want to enable `beacon_disable_sendbeacon` as
    // `sendBeacon()` does not support credentials.
    beacon_with_credentials: false,

    // Disables navigator.sendBeacon() support
    beacon_disable_sendbeacon: false,

    // Strip out everything except last two parts of hostname.
    // This doesn't work well for domains that end with a country tld,
    // but we allow the developer to override site_domain for that.
    // You can disable all cookies by setting site_domain to a falsy value.
    site_domain: w.location.hostname.
      replace(/.*?([^.]+\.[^.]+)\.?$/, "$1").
      toLowerCase(),

    // User's ip address determined on the server.  Used for the BW cookie.
    user_ip: "",

    // Whether or not to send beacons on page load
    autorun: true,

    // Whether or not we've sent a page load beacon
    hasSentPageLoadBeacon: false,

    // document.referrer
    r: undefined,

    // strip_query_string: false,

    // onloadfired: false,

    // handlers_attached: false,

    // waiting_for_config: false,

    // All Boomerang cookies will be created with SameSite=Lax by default
    same_site_cookie: "Lax",

    // All Boomerang cookies will be without Secure attribute by default
    secure_cookie: false,

    // Sometimes we would like to be able to set the SameSite=None from a Boomerang plugin
    forced_same_site_cookie_none: false,

    // Navigator User Agent data object holding Architecture, Model and Platform information from Client Hints API
    userAgentData: undefined,

    // Client hints use for Architecture, Model and Platform detail is disabled by default
    request_client_hints: false,

    // Disables all Unload handlers and Unload beacons
    no_unload: false,

    events: {
      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when the page is usable by the user.
       *
       * By default this is fired when `window.onload` fires, but if you
       * set `autorun` to false when calling {@link BOOMR.init}, then you
       * must explicitly fire this event by calling {@link BOOMR#event:page_ready}.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onload}
       * @event BOOMR#page_ready
       * @property {Event} [event] Event triggering the page_ready
       */
      "page_ready": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired just before the browser unloads the page.
       *
       * The first event of `window.pagehide`, `window.beforeunload`,
       * or `window.unload` will trigger this.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/Events/pagehide}
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onbeforeunload}
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onunload}
       * @event BOOMR#page_unload
       */
      "page_unload": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired before the document is about to be unloaded.
       *
       * `window.beforeunload` will trigger this.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onbeforeunload}
       * @event BOOMR#before_unload
       */
      "before_unload": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired on `document.DOMContentLoaded`.
       *
       * The `DOMContentLoaded` event is fired when the initial HTML document
       * has been completely loaded and parsed, without waiting for stylesheets,
       * images, and subframes to finish loading
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/Events/DOMContentLoaded}
       * @event BOOMR#dom_loaded
       */
      "dom_loaded": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired on `document.visibilitychange`.
       *
       * The `visibilitychange` event is fired when the content of a tab has
       * become visible or has been hidden.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/Events/visibilitychange}
       * @event BOOMR#visibility_changed
       */
      "visibility_changed": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when the `visibilityState` of the document has changed from
       * `prerender` to `visible`
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/Events/visibilitychange}
       * @event BOOMR#prerender_to_visible
       */
      "prerender_to_visible": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when a beacon is about to be sent.
       *
       * The subscriber can still add variables to the beacon at this point,
       * either by modifying the `vars` paramter or calling {@link BOOMR.addVar}.
       *
       * @event BOOMR#before_beacon
       * @property {object} vars Beacon variables
       */
      "before_beacon": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when a beacon was sent.
       *
       * The beacon variables cannot be modified at this point.  Any calls
       * to {@link BOOMR.addVar} or {@link BOOMR.removeVar} will apply to the
       * next beacon.
       *
       * Also known as `onbeacon`.
       *
       * @event BOOMR#beacon
       * @property {object} vars Beacon variables
       */
      "beacon": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when the page load beacon has been sent.
       *
       * This event should only happen once on a page.  It does not apply
       * to SPA soft navigations.
       *
       * @event BOOMR#page_load_beacon
       * @property {object} vars Beacon variables
       */
      "page_load_beacon": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when an XMLHttpRequest has finished, or, if something calls
       * {@link BOOMR.responseEnd}.
       *
       * @event BOOMR#xhr_load
       * @property {object} data Event data
       */
      "xhr_load": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when the `click` event has happened on the `document`.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onclick}
       * @event BOOMR#click
       */
      "click": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when any `FORM` element is submitted.
       *
       * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/submit}
       * @event BOOMR#form_submit
       */
      "form_submit": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever new configuration data is applied via {@link BOOMR.init}.
       *
       * Also known as `onconfig`.
       *
       * @event BOOMR#config
       * @property {object} data Configuration data
       */
      "config": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever `XMLHttpRequest.open` is called.
       *
       * This event will only happen if {@link BOOMR.plugins.AutoXHR} is enabled.
       *
       * @event BOOMR#xhr_init
       * @property {string} type XHR type ("xhr")
       */
      "xhr_init": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever a SPA plugin is about to track a new navigation.
       *
       * @event BOOMR#spa_init
       * @property {object[]} parameters Navigation type (`spa` or `spa_hard`), URL and timings
       */
      "spa_init": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever a SPA navigation is complete.
       *
       * @event BOOMR#spa_navigation
       * @property {object[]} parameters Timings
       */
      "spa_navigation": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever a SPA navigation is cancelled.
       *
       * @event BOOMR#spa_cancel
       */
      "spa_cancel": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever `XMLHttpRequest.send` is called.
       *
       * This event will only happen if {@link BOOMR.plugins.AutoXHR} is enabled.
       *
       * @event BOOMR#xhr_send
       * @property {object} xhr `XMLHttpRequest` object
       */
      "xhr_send": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever and `XMLHttpRequest` has an error (if its `status` is
       * set).
       *
       * This event will only happen if {@link BOOMR.plugins.AutoXHR} is enabled.
       *
       * Also known as `onxhrerror`.
       *
       * @event BOOMR#xhr_error
       * @property {object} data XHR data
       */
      "xhr_error": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever a page error has happened.
       *
       * This event will only happen if {@link BOOMR.plugins.Errors} is enabled.
       *
       * Also known as `onerror`.
       *
       * @event BOOMR#error
       * @property {object} err Error
       */
      "error": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever connection information changes via the
       * Network Information API.
       *
       * This event will only happen if {@link BOOMR.plugins.Mobile} is enabled.
       *
       * @event BOOMR#netinfo
       * @property {object} connection `navigator.connection`
       */
      "netinfo": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired whenever a Rage Click is detected.
       *
       * This event will only happen if {@link BOOMR.plugins.Continuity} is enabled.
       *
       * @event BOOMR#rage_click
       * @property {Event} e Event
       */
      "rage_click": [],

      /**
       * Boomerang event, subscribe via {@link BOOMR.subscribe}.
       *
       * Fired when an early beacon is about to be sent.
       *
       * The subscriber can still add variables to the early beacon at this point
       * by calling {@link BOOMR.addVar}.
       *
       * This event will only happen if {@link BOOMR.plugins.Early} is enabled.
       *
       * @event BOOMR#before_early_beacon
       * @property {object} data Event data
       */
      "before_early_beacon": []
    },

    /**
     * Public events
     */
    public_events: {
      /**
       * Public event (fired on `document`), and can be subscribed via
       * `document.addEventListener("onBeforeBoomerangBeacon", ...)` or
       * `document.attachEvent("onpropertychange", ...)`.
       *
       * Maps to {@link BOOMR#event:before_beacon}
       *
       * @event document#onBeforeBoomerangBeacon
       * @property {object} vars Beacon variables
       */
      "before_beacon": "onBeforeBoomerangBeacon",

      /**
       * Public event (fired on `document`), and can be subscribed via
       * `document.addEventListener("onBoomerangBeacon", ...)` or
       * `document.attachEvent("onpropertychange", ...)`.
       *
       * Maps to {@link BOOMR#event:before_beacon}
       *
       * @event document#onBoomerangBeacon
       * @property {object} vars Beacon variables
       */
      "beacon": "onBoomerangBeacon",

      /**
       * Public event (fired on `document`), and can be subscribed via
       * `document.addEventListener("onBoomerangLoaded", ...)` or
       * `document.attachEvent("onpropertychange", ...)`.
       *
       * Fired when {@link BOOMR} has loaded and can be used.
       *
       * @event document#onBoomerangLoaded
       */
      "onboomerangloaded": "onBoomerangLoaded"
    },

    /**
     * Maps old event names to their updated name
     */
    translate_events: {
      "onbeacon": "beacon",
      "onconfig": "config",
      "onerror": "error",
      "onxhrerror": "xhr_error"
    },

    /**
     * Number of page_unload or before_unload callbacks registered
     */
    unloadEventsCount: 0,

    /**
     * Number of page_unload or before_unload callbacks called
     */
    unloadEventCalled: 0,

    listenerCallbacks: {},

    vars: {},
    singleBeaconVars: {},

    /**
     * Variable priority lists:
     * -1 = first
     *  1 = last
     */
    varPriority: {
      "-1": {},
      "1": {}
    },

    errors: {},

    disabled_plugins: {},

    localStorageSupported: false,
    LOCAL_STORAGE_PREFIX: "_boomr_",

    /**
     * Native functions that were overwritten and should be restored when
     * the Boomerang IFRAME is unloaded
     */
    nativeOverwrites: [],

    xb_handler: function(type) {
      return function(ev) {
        var target;

        if (!ev) {
          ev = w.event;
        }

        if (ev.target) {
          target = ev.target;
        }
        else if (ev.srcElement) {
          target = ev.srcElement;
        }

        if (target.nodeType === 3) {
          // defeat Safari bug
          target = target.parentNode;
        }

        // don't capture events on flash objects
        // because of context slowdowns in PepperFlash
        if (target &&
            target.nodeName &&
            target.nodeName.toUpperCase() === "OBJECT" &&
            target.type === "application/x-shockwave-flash") {
          return;
        }

        impl.fireEvent(type, target);
      };
    },

    clearEvents: function() {
      var eventName;

      for (eventName in this.events) {
        if (this.events.hasOwnProperty(eventName)) {
          this.events[eventName] = [];
        }
      }
    },

    clearListeners: function() {
      var type, i;

      for (type in impl.listenerCallbacks) {
        if (impl.listenerCallbacks.hasOwnProperty(type)) {
          // remove all callbacks -- removeListener is guaranteed
          // to remove the element we're calling with
          while (impl.listenerCallbacks[type].length) {
            BOOMR.utils.removeListener(
              impl.listenerCallbacks[type][0].el,
              type,
              impl.listenerCallbacks[type][0].fn);
          }
        }
      }

      impl.listenerCallbacks = {};
    },

    fireEvent: function(e_name, data) {
      var i, handler, handlers, handlersLen;

      e_name = e_name.toLowerCase();

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("fire_event");
      BOOMR.utils.mark("fire_event:" + e_name + ":start");
      /* END_DEBUG */

      // translate old names
      if (this.translate_events[e_name]) {
        e_name = this.translate_events[e_name];
      }

      if (!this.events.hasOwnProperty(e_name)) {
        return;
      }

      if (this.public_events.hasOwnProperty(e_name)) {
        dispatchEvent(this.public_events[e_name], data);
      }

      handlers = this.events[e_name];

      // Before we fire any event listeners, let's call real_sendBeacon() to flush
      // any beacon that is being held by the setImmediate.
      if (e_name !== "before_beacon" && e_name !== "beacon" && e_name !== "before_early_beacon") {
        BOOMR.real_sendBeacon();
      }

      // only call handlers at the time of fireEvent (and not handlers that are
      // added during this callback to avoid an infinite loop)
      handlersLen = handlers.length;
      for (i = 0; i < handlersLen; i++) {
        try {
          handler = handlers[i];
          handler.fn.call(handler.scope, data, handler.cb_data);
        }
        catch (err) {
          BOOMR.addError(err, "fireEvent." + e_name + "<" + i + ">");
        }
      }

      // remove any 'once' handlers now that we've fired all of them
      for (i = 0; i < handlersLen; i++) {
        if (handlers[i].once) {
          handlers.splice(i, 1);
          handlersLen--;
          i--;
        }
      }

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("fire_event:" + e_name + ":end");
      BOOMR.utils.measure(
        "fire_event:" + e_name,
        "fire_event:" + e_name + ":start",
        "fire_event:" + e_name + ":end");
      /* END_DEBUG */

      return;
    },

    spaNavigation: function() {
      // a SPA navigation occured, force onloadfired to true
      impl.onloadfired = true;
    },

    /**
     * Determines whether a beacon URL is allowed based on
     * `beacon_urls_allowed` config
     *
     * @param {string} url URL to test
     *
     */
    beaconUrlAllowed: function(url) {
      if (!impl.beacon_urls_allowed || impl.beacon_urls_allowed.length === 0) {
        return true;
      }

      for (var i = 0; i < impl.beacon_urls_allowed.length; i++) {
        var regEx = new RegExp(impl.beacon_urls_allowed[i]);

        if (regEx.exec(url)) {
          return true;
        }
      }

      return false;
    },

    /**
     * Checks browser for localStorage support
     */
    checkLocalStorageSupport: function() {
      var name = impl.LOCAL_STORAGE_PREFIX + "clss";

      impl.localStorageSupported = false;

      // Browsers with cookies disabled or in private/incognito mode may throw an
      // error when accessing the localStorage variable
      try {
        // we need JSON and localStorage support
        if (!w.JSON || !w.localStorage) {
          return;
        }

        w.localStorage.setItem(name, name);
        impl.localStorageSupported = (w.localStorage.getItem(name) === name);
        w.localStorage.removeItem(name);
      }
      catch (ignore) {
        impl.localStorageSupported = false;
      }
    },

    /**
     * Fired when the Boomerang IFRAME is unloaded.
     *
     * If Boomerang was loaded into the root document, this code
     * will not run.
     */
    onFrameUnloaded: function() {
      var i, prop;

      BOOMR.isUnloaded = true;

      // swap the original function back in for any overwrites
      for (i = 0; i < impl.nativeOverwrites.length; i++) {
        prop = impl.nativeOverwrites[i];

        prop.obj[prop.functionName] = prop.origFn;
      }

      impl.nativeOverwrites = [];
    }
  };

  // We create a boomr object and then copy all its properties to BOOMR so that
  // we don't overwrite anything additional that was added to BOOMR before this
  // was called... for example, a plugin.
  boomr = {
    /**
     * The timestamp when boomerang.js showed up on the page.
     *
     * This is the value of `BOOMR_start` we set earlier.
     * @type {TimeStamp}
     *
     * @memberof BOOMR
     */
    t_start: BOOMR_start,

    /**
     * When the Boomerang plugins have all run.
     *
     * This value is generally set in zzz-last-plugin.js.
     * @type {TimeStamp}
     *
     * @memberof BOOMR
     */
    t_end: undefined,

    /**
     * URL of boomerang.js.
     *
     * @type {string}
     *
     * @memberof BOOMR
     */
    url: "",

    /**
     * (Optional) URL of configuration file
     *
     * @type {string}
     *
     * @memberof BOOMR
     */
    config_url: null,

    /**
     * Whether or not Boomerang was loaded after the `onload` event.
     *
     * @type {boolean}
     *
     * @memberof BOOMR
     */
    loadedLate: false,

    /**
     * Current number of beacons sent.
     *
     * Will be incremented and added to outgoing beacon as `n`.
     *
     * @type {number}
     *
     */
    beaconsSent: 0,

    /**
     * Whether or not Boomerang thinks it has been unloaded (if it was
     * loaded in an IFRAME)
     *
     * @type {boolean}
     */
    isUnloaded: false,

    /**
     * Whether or not we're in the middle of building a beacon.
     *
     * If so, the code desiring to send a beacon should wait until the beacon
     * event and try again.  At that point, it should set this flag to true.
     *
     * @type {boolean}
     */
    beaconInQueue: false,

    /*
     * Cache of cookies set
     */
    cookies: {},

    /**
     * Whether or not we've tested cookie setting
     */
    testedCookies: false,

    /**
     * Constants visible to the world
     * @class BOOMR.constants
     */
    constants: {
      /**
       * SPA beacon types
       *
       * @type {string[]}
       *
       * @memberof BOOMR.constants
       */
      BEACON_TYPE_SPAS: ["spa", "spa_hard"],

      /**
       * Maximum GET URL length.
       * Using 2000 here as a de facto maximum URL length based on:
        * https://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url-in-different-browsers
       *
       * @type {number}
       *
       * @memberof BOOMR.constants
       */
      MAX_GET_LENGTH: 2000
    },

    /**
     * Session data
     * @class BOOMR.session
     */
    session: {
      /**
       * Session Domain.
       *
       * You can disable all cookies by setting site_domain to a falsy value.
       *
       * @type {string}
       *
       * @memberof BOOMR.session
       */
      domain: impl.site_domain,

      /**
       * Session ID.  This will be randomly generated in the client but may
       * be overwritten by the server if not set.
       *
       * @type {string}
       *
       * @memberof BOOMR.session
       */
      ID: undefined,

      /**
       * Session start time.
       *
       * @type {TimeStamp}
       *
       * @memberof BOOMR.session
       */
      start: undefined,

      /**
       * Session length (number of pages)
       *
       * @type {number}
       *
       * @memberof BOOMR.session
       */
      length: 0,

      /**
       * Session enabled (Are session cookies enabled?)
       *
       * @type {boolean}
       *
       * @memberof BOOMR.session
       */
      enabled: true
    },

    /**
     * @class BOOMR.utils
     */
    utils: {
      /**
       * Determines whether or not the browser has `postMessage` support
       *
       * @returns {boolean} True if supported
       */
      hasPostMessageSupport: function() {
        if (!w.postMessage || typeof w.postMessage !== "function" && typeof w.postMessage !== "object") {
          return false;
        }

        return true;
      },

      /**
       * Converts an object to a string.
       *
       * @param {object} o Object
       * @param {string} separator Member separator
       * @param {number} nest_level Number of levels to recurse
       *
       * @returns {string} String representation of the object
       *
       * @memberof BOOMR.utils
       */
      objectToString: function(o, separator, nest_level) {
        var value = [],
            k;

        if (!o || typeof o !== "object") {
          return o;
        }

        if (separator === undefined) {
          separator = "\n\t";
        }

        if (!nest_level) {
          nest_level = 0;
        }

        if (BOOMR.utils.isArray(o)) {
          for (k = 0; k < o.length; k++) {
            if (nest_level > 0 && o[k] !== null && typeof o[k] === "object") {
              value.push(
                this.objectToString(
                  o[k],
                  separator + (separator === "\n\t" ? "\t" : ""),
                  nest_level - 1
                )
              );
            }
            else {
              if (separator === "&") {
                value.push(encodeURIComponent(o[k]));
              }
              else {
                value.push(o[k]);
              }
            }
          }

          separator = ",";
        }
        else {
          for (k in o) {
            if (Object.prototype.hasOwnProperty.call(o, k)) {
              if (nest_level > 0 && o[k] !== null && typeof o[k] === "object") {
                value.push(encodeURIComponent(k) + "=" +
                  this.objectToString(
                    o[k],
                    separator + (separator === "\n\t" ? "\t" : ""),
                    nest_level - 1
                  )
                );
              }
              else {
                if (separator === "&") {
                  value.push(encodeURIComponent(k) + "=" + encodeURIComponent(o[k]));
                }
                else {
                  value.push(k + "=" + o[k]);
                }
              }
            }
          }
        }

        return value.join(separator);
      },

      /**
       * Gets the cached value of the cookie identified by `name`.
       *
       * @param {string} name Cookie name
       *
       * @returns {string|undefined} Cookie value, if set.
       *
       * @memberof BOOMR.utils
       */
      getCookie: function(name) {
        var cookieVal;

        if (!name) {
          return null;
        }

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("get_cookie");
        /* END_DEBUG */

        if (typeof BOOMR.cookies[name] !== "undefined") {
          // a cached value of false indicates that the value doesn't exist, if so,
          // return undefined per the API
          return BOOMR.cookies[name] === false ? undefined : BOOMR.cookies[name];
        }

        // unknown value
        cookieVal = this.getRawCookie(name);

        if (typeof cookieVal === "undefined") {
          // set to false to indicate we've attempted to get this cookie
          BOOMR.cookies[name] = false;

          // but return undefined per the API
          return undefined;
        }

        BOOMR.cookies[name] = cookieVal;

        return BOOMR.cookies[name];
      },

      /**
       * Gets the value of the cookie identified by `name`.
       *
       * @param {string} name Cookie name
       *
       * @returns {string|null} Cookie value, if set.
       *
       * @memberof BOOMR.utils
       */
      getRawCookie: function(name) {
        if (!name) {
          return null;
        }

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("get_raw_cookie");
        /* END_DEBUG */

        name = " " + name + "=";

        var i, cookies;

        cookies = " " + d.cookie + ";";

        if ((i = cookies.indexOf(name)) >= 0) {
          i += name.length;

          return cookies.substring(i, cookies.indexOf(";", i)).replace(/^"/, "").replace(/"$/, "");
        }
      },

      /**
       * Sets the cookie named `name` to the serialized value of `subcookies`.
       *
       * @param {string} name The name of the cookie
       * @param {object} subcookies Key/value pairs to write into the cookie.
       * These will be serialized as an & separated list of URL encoded key=value pairs.
       * @param {number} max_age Lifetime in seconds of the cookie.
       * Set this to 0 to create a session cookie that expires when
       * the browser is closed. If not set, defaults to 0.
       *
       * @returns {boolean} True if the cookie was set successfully
       *
       * @example
       * BOOMR.utils.setCookie("RT", { s: t_start, r: url });
       *
       * @memberof BOOMR.utils
       */
      setCookie: function(name, subcookies, max_age) {
        var value, nameval, savedval, c, exp;

        if (!name || !BOOMR.session.domain || typeof subcookies === "undefined") {
          BOOMR.debug("Invalid parameters or site domain: " + name + "/" + subcookies + "/" + BOOMR.session.domain);

          BOOMR.addVar("nocookie", 1);

          return false;
        }

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("set_cookie");
        /* END_DEBUG */

        value = this.objectToString(subcookies, "&");

        if (value === BOOMR.cookies[name]) {
          // no change
          return true;
        }

        nameval = name + "=\"" + value + "\"";

        if (nameval.length < 500) {
          c = [nameval, "path=/", "domain=" + BOOMR.session.domain];

          if (typeof max_age === "number") {
            exp = new Date();
            exp.setTime(exp.getTime() + max_age * 1000);
            exp = exp.toGMTString();
            c.push("expires=" + exp);
          }

          var extraAttributes = this.getSameSiteAttributeParts();

          /**
           * 1. We check if the Secure attribute wasn't added already because SameSite=None will force adding it.
           * 2. We check the current protocol because if we are on HTTP and we try to create a secure cookie with
           *    SameSite=Strict then a cookie will be created with SameSite=Lax.
           */
          if (location.protocol === "https:" &&
              impl.secure_cookie === true &&
              extraAttributes.indexOf("Secure") === -1) {
            extraAttributes.push("Secure");
          }

          // add extra attributes
          c = c.concat(extraAttributes);

          /* BEGIN_DEBUG */
          BOOMR.utils.mark("set_cookie_real");
          /* END_DEBUG */

          // set the cookie
          d.cookie = c.join("; ");

          // we only need to test setting the cookie once
          if (BOOMR.testedCookies) {
            // only cache this cookie value if the expiry is in the future
            if (typeof max_age !== "number" || max_age > 0) {
              BOOMR.cookies[name] = value;
            }
            else {
              // the cookie is going to expire right away, don't cache it
              BOOMR.cookies[name] = undefined;
            }

            return true;
          }

          // unset the cached cookie value, in case the set doesn't work
          BOOMR.cookies[name] = undefined;

          // confirm cookie was set (could be blocked by user's settings, etc.)
          savedval = this.getRawCookie(name);

          // the saved cookie should be the same or undefined in the case of removeCookie
          if (value === savedval ||
              (typeof savedval === "undefined" && typeof max_age === "number" && max_age <= 0)) {
            // re-set the cached value
            BOOMR.cookies[name] = value;

            // note we've saved successfully
            BOOMR.testedCookies = true;

            BOOMR.removeVar("nocookie");

            return true;
          }

          BOOMR.warn("Saved cookie value doesn't match what we tried to set:\n" + value + "\n" + savedval);
        }
        else {
          BOOMR.warn("Cookie too long: " + nameval.length + " " + nameval);
        }

        BOOMR.addVar("nocookie", 1);

        return false;
      },

      /**
       * Parse a cookie string returned by {@link BOOMR.utils.getCookie} and
       * split it into its constituent subcookies.
       *
       * @param {string} cookie Cookie value
       *
       * @returns {object} On success, an object of key/value pairs of all
       * sub cookies. Note that some subcookies may have empty values.
       * `null` if `cookie` was not set or did not contain valid subcookies.
       *
       * @memberof BOOMR.utils
       */
      getSubCookies: function(cookie) {
        var cookies_a,
            i, l, kv,
            gotcookies = false,
            cookies = {};

        if (!cookie) {
          return null;
        }

        if (typeof cookie !== "string") {
          BOOMR.debug("TypeError: cookie is not a string: " + typeof cookie);

          return null;
        }

        cookies_a = cookie.split("&");

        for (i = 0, l = cookies_a.length; i < l; i++) {
          kv = cookies_a[i].split("=");

          if (kv[0]) {
            // just in case there's no value
            kv.push("");
            cookies[decodeURIComponent(kv[0])] = decodeURIComponent(kv[1]);
            gotcookies = true;
          }
        }

        return gotcookies ? cookies : null;
      },

      /**
       * Removes the cookie identified by `name` by nullifying its value,
       * and making it a session cookie.
       *
       * @param {string} name Cookie name
       *
       * @memberof BOOMR.utils
       */
      removeCookie: function(name) {
        return this.setCookie(name, {}, -86400);
      },

      /**
       * Depending on Boomerang configuration and checks of current protocol and
       * compatible browsers the logic below will provide an array of cookie
       * attributes that are needed for a successful creation of a cookie that
       * contains the SameSite attribute.
       *
       * How it works:
       * 1. We read the Boomerang configuration key `same_site_cookie` where
       *    one of the following values `None`, `Lax` or `Strict` is expected.
       * 2. A configuration value of `same_site_cookie` will be read in case-insensitive
       *    manner. E.g. `Lax`, `lax` and `lAx` will produce same result - `SameSite=Lax`.
       * 3. If a `same_site_cookie` configuration value is not specified a cookie
       *    will be created with `SameSite=Lax`.
       * 4. If a `same_site_cookie` configuration value does't match any of
       *    `None`, `Lax` or `Strict` then a cookie will be created with `SameSite=Lax`.
       * 5. The `Secure` cookie attribute will be added when a cookie is created
       *    with `SameSite=None`.
       * 6. It's possible that a Boomerang plugin or external code may need cookies
       *    to be created with `SameSite=None`. In such cases we check a special
       *    flag `forced_same_site_cookie_none`. If the value of this flag is equal to `true`
       *    then the `same_site_cookie` value will be ignored and Boomerang cookies
       *    will be created with `SameSite=None`.
       *
       * SameSite=None - INCOMPATIBILITIES and EXCEPTIONS:
       *
       * There are known problems with older browsers where cookies created
       * with `SameSite=None` are `dropped` or created with `SameSite=Strict`.
       * Reference: https://www.chromium.org/updates/same-site/incompatible-clients
       *
       * 1. If we detect a browser that can't create safely a cookie with `SameSite=None`
       *    then Boomerang will create a cookie without the `SameSite` attribute.
       * 2. A cookie with `SameSite=None` can be created only over `HTTPS` connection.
       *    If current connection is `HTTP` then a cookie will be created
       *    without the `SameSite` attribute.
       *
       *
       * @returns {Array} of cookie attributes used for setting a cookie with SameSite attribute
       *
       * @memberof BOOMR.utils
       */
      getSameSiteAttributeParts: function() {
        var sameSiteMode = impl.same_site_cookie.toUpperCase();

        if (impl.forced_same_site_cookie_none) {
          sameSiteMode = "NONE";
        }

        if (sameSiteMode === "LAX") {
          return ["SameSite=Lax"];
        }

        if (sameSiteMode === "NONE") {
          if (location.protocol === "https:" && this.isCurrentUASameSiteNoneCompatible()) {
            return ["SameSite=None", "Secure"];
          }

          // Fallback to browser's default
          return [];
        }

        if (sameSiteMode === "STRICT") {
          return ["SameSite=Strict"];
        }

        return ["SameSite=Lax"];
      },

      /**
       * Retrieve items from localStorage
       *
       * @param {string} name Name of storage
       *
       * @returns {object|null} Returns object retrieved from localStorage.
       *                       Returns undefined if not found or expired.
       *                       Returns null if parameters are invalid or an error occured
       *
       * @memberof BOOMR.utils
       */
      getLocalStorage: function(name) {
        var value, data;

        if (!name || !impl.localStorageSupported) {
          return null;
        }

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("get_local_storage");
        /* END_DEBUG */

        try {
          value = w.localStorage.getItem(impl.LOCAL_STORAGE_PREFIX + name);

          if (value === null) {
            return undefined;
          }

          data = w.JSON.parse(value);
        }
        catch (e) {
          BOOMR.warn(e);

          return null;
        }

        if (!data || typeof data.items !== "object") {
          // Items are invalid
          this.removeLocalStorage(name);

          return null;
        }

        if (typeof data.expires === "number") {
          if (BOOMR.now() >= data.expires) {
            // Items are expired
            this.removeLocalStorage(name);

            return undefined;
          }
        }

        return data.items;
      },

      /**
       * Saves items in localStorage
       * The value stored in localStorage will be a JSON string representation of {"items": items, "expiry": expiry}
       * where items is the object we're saving and expiry is an optional epoch number of when the data is to be
       * considered expired
       *
       * @param {string} name Name of storage
       * @param {object} items Items to be saved
       * @param {number} max_age Age in seconds before items are to be considered expired
       *
       * @returns {boolean} True if the localStorage was set successfully
       *
       * @memberof BOOMR.utils
       */
      setLocalStorage: function(name, items, max_age) {
        var data, value, savedval;

        if (!name || !impl.localStorageSupported || typeof items !== "object") {
          return false;
        }

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("set_local_storage");
        /* END_DEBUG */

        data = {"items": items};

        if (typeof max_age === "number") {
          data.expires = BOOMR.now() + (max_age * 1000);
        }

        value = w.JSON.stringify(data);

        if (value.length < 50000) {
          try {
            w.localStorage.setItem(impl.LOCAL_STORAGE_PREFIX + name, value);
            // confirm storage was set (could be blocked by user's settings, etc.)
            savedval = w.localStorage.getItem(impl.LOCAL_STORAGE_PREFIX + name);

            if (value === savedval) {
              return true;
            }
          }
          catch (ignore) {
            // Empty
          }

          BOOMR.warn("Saved storage value doesn't match what we tried to set:\n" + value + "\n" + savedval);
        }
        else {
          BOOMR.warn("Storage items too large: " + value.length + " " + value);
        }

        return false;
      },

      /**
       * Remove items from localStorage
       *
       * @param {string} name Name of storage
       *
       * @returns {boolean} True if item was removed from localStorage.
       *
       * @memberof BOOMR.utils
       */
      removeLocalStorage: function(name) {
        if (!name || !impl.localStorageSupported) {
          return false;
        }
        try {
          w.localStorage.removeItem(impl.LOCAL_STORAGE_PREFIX + name);

          return true;
        }
        catch (ignore) {
          // Empty
        }

        return false;
      },

      /**
       * Cleans up a URL by removing the query string (if configured), and
       * limits the URL to the specified size.
       *
       * @param {string} url URL to clean
       * @param {number} urlLimit Maximum size, in characters, of the URL
       *
       * @returns {string} Cleaned up URL
       *
       * @memberof BOOMR.utils
       */
      cleanupURL: function(url, urlLimit) {
        if (!url || BOOMR.utils.isArray(url)) {
          return "";
        }

        if (impl.strip_query_string) {
          url = url.replace(/\?.*/, "?qs-redacted");
        }

        if (typeof urlLimit !== "undefined" && url && url.length > urlLimit) {
          // We need to break this URL up.  Try at the query string first.
          var qsStart = url.indexOf("?");

          if (qsStart !== -1 && qsStart < urlLimit) {
            url = url.substr(0, qsStart) + "?...";
          }
          else {
            // No query string, just stop at the limit
            url = url.substr(0, urlLimit - 3) + "...";
          }
        }

        return url;
      },

      /**
       * Gets the URL with the query string replaced with a hash of its contents.
       *
       * @param {string} url URL
       * @param {boolean} stripHash Whether or not to strip the hash
       *
       * @returns {string} URL with query string hashed
       *
       * @memberof BOOMR.utils
       */
      hashQueryString: function(url, stripHash) {
        if (!url) {
          return url;
        }

        if (!url.match) {
          BOOMR.addError("TypeError: Not a string", "hashQueryString", typeof url);

          return "";
        }

        if (url.match(/^\/\//)) {
          url = location.protocol + url;
        }

        if (!url.match(/^(https?|file):/)) {
          BOOMR.error("Passed in URL is invalid: " + url);

          return "";
        }

        if (stripHash) {
          url = url.replace(/#.*/, "");
        }

        return url.replace(/\?([^#]*)/, function(m0, m1) {
          return "?" + (m1.length > 10 ? BOOMR.utils.hashString(m1) : m1);
        });
      },

      /**
       * Sets the object's properties if anything in config matches
       * one of the property names.
       *
       * @param {object} o The plugin's `impl` object within which it stores
       * all its configuration and private properties
       * @param {object} config The config object passed in to the plugin's
       * `init()` method.
       * @param {string} plugin_name The plugin's name in the {@link BOOMR.plugins} object.
       * @param {string[]} properties An array containing a list of all configurable
       * properties that this plugin has.
       *
       * @returns {boolean} True if a property was set
       *
       * @memberof BOOMR.utils
       */
      pluginConfig: function(o, config, plugin_name, properties) {
        var i,
            props = 0;

        if (!config || !config[plugin_name]) {
          return false;
        }

        for (i = 0; i < properties.length; i++) {
          if (config[plugin_name][properties[i]] !== undefined) {
            o[properties[i]] = config[plugin_name][properties[i]];
            props++;
          }
        }

        return (props > 0);
      },

      /**
       * `filter` for arrays
       *
       * @param {Array} array The array to iterate over.
       * @param {Function} predicate The function invoked per iteration.
       *
       * @returns {Array} Returns the new filtered array.
       *
       * @memberof BOOMR.utils
       */
      arrayFilter: function(array, predicate) {
        var result = [];

        if (!(this.isArray(array) || (array && typeof array.length === "number")) ||
            typeof predicate !== "function") {
          return result;
        }

        if (typeof array.filter === "function") {
          result = array.filter(predicate);
        }
        else {
          var index = -1,
              length = array.length,
              value;

          while (++index < length) {
            value = array[index];

            if (predicate(value, index, array)) {
              result[result.length] = value;
            }
          }
        }

        return result;
      },

      /**
       * `find` for Arrays
       *
       * @param {Array} array The array to iterate over
       * @param {Function} predicate The function invoked per iteration
       *
       * @returns {Array} Returns the value of first element that satisfies
       * the predicate
       *
       * @memberof BOOMR.utils
       */
      arrayFind: function(array, predicate) {
        if (!(this.isArray(array) || (array && typeof array.length === "number")) ||
            typeof predicate !== "function") {
          return undefined;
        }

        if (typeof array.find === "function") {
          return array.find(predicate);
        }
        else {
          var index = -1,
              length = array.length,
              value;

          while (++index < length) {
            value = array[index];

            if (predicate(value, index, array)) {
              return value;
            }
          }

          return undefined;
        }
      },

      /**
       * MutationObserver feature detection
       *
       * Always returns false for IE 11 due several bugs in it's implementation that MS flagged as Won't Fix.
       * In IE11, XHR responseXML might be malformed if MO is enabled (where extra newlines get added in nodes
       * with UTF-8 content).
       *
       * Another IE 11 MO bug can cause the process to crash when certain mutations occur.
       *
       * For the process crash issue, see https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/8137215/
       * and
       * https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/15167323/
       *
       * @returns {boolean} Returns true if MutationObserver is supported.
       *
       * @memberof BOOMR.utils
       */
      isMutationObserverSupported: function() {
        // We can only detect IE 11 bugs by UA sniffing.
        var ie11 = (w &&
          w.navigator &&
          !w.navigator.userAgentData &&
          w.navigator.userAgent &&
          w.navigator.userAgent.match(/Trident.*rv[ :]*11\./));

        return (!ie11 && w && w.MutationObserver && typeof w.MutationObserver === "function");
      },

      /**
       * The callback function may return a falsy value to disconnect the
       * observer after it returns, or a truthy value to keep watching for
       * mutations. If the return value is numeric and greater than 0, then
       * this will be the new timeout. If it is boolean instead, then the
       * timeout will not fire any more so the caller MUST call disconnect()
       * at some point.
       *
       * @callback BOOMR~addObserverCallback
       * @param {object[]} mutations List of mutations detected by the observer or `undefined` if the observer timed out
       * @param {object} callback_data Is the passed in `callback_data` parameter without modifications
       */

      /**
       * Add a MutationObserver for a given element and terminate after `timeout`ms.
       *
       * @param {DOMElement} el DOM element to watch for mutations
       * @param {MutationObserverInit} config MutationObserverInit object
       *   (https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver#MutationObserverInit)
       * @param {number} timeout Number of milliseconds of no mutations after which the observer should be
       *   automatically disconnected.
       *   If set to a falsy value, the observer will wait indefinitely for Mutations.
       * @param {BOOMR~addObserverCallback} callback Callback function to call either on timeout or if mutations
       *   are detected.
       * @param {object} callback_data Any data to be passed to the callback function as its second parameter.
       * @param {object} callback_ctx An object that represents the `this` object of the `callback` method.
       * Leave unset the callback function is not a method of an object.
       *
       * @returns {object|null}
       * - `null` if a MutationObserver could not be created OR
       * - An object containing the observer and the timer object:
       *   `{ observer: <MutationObserver>, timer: <Timeout Timer if any> }`
       * - The caller can use this to disconnect the observer at any point
       *   by calling `retval.observer.disconnect()`
       * - Note that the caller should first check to see if `retval.observer`
       *   is set before calling `disconnect()` as it may have been cleared automatically.
       *
       * @memberof BOOMR.utils
       */
      addObserver: function(el, config, timeout, callback, callback_data, callback_ctx) {
        var MO, zs,
            o = {observer: null, timer: null};

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("add_observer");
        /* END_DEBUG */

        if (!this.isMutationObserverSupported() || !callback || !el) {
          return null;
        }

        function done(mutations) {
          var run_again = false;

          /* BEGIN_DEBUG */
          BOOMR.utils.mark("mutation_observer_callback");
          /* END_DEBUG */

          if (o.timer) {
            clearTimeout(o.timer);
            o.timer = null;
          }

          if (callback) {
            run_again = callback.call(callback_ctx, mutations, callback_data);

            if (!run_again) {
              callback = null;
            }
          }

          if (!run_again && o.observer) {
            o.observer.disconnect();
            o.observer = null;
          }

          if (typeof run_again === "number" && run_again > 0) {
            o.timer = setTimeout(done, run_again);
          }
        }

        MO = w.MutationObserver;

        // if the site uses Zone.js then get the native MutationObserver
        if (w.Zone && typeof w.Zone.__symbol__ === "function") {
          zs = w.Zone.__symbol__("MutationObserver");

          if (zs && typeof zs === "string" && w.hasOwnProperty(zs) && typeof w[zs] === "function") {
            BOOMR.debug("Detected Zone.js, using native MutationObserver");
            MO = w[zs];
          }
        }

        o.observer = new MO(done);

        if (timeout) {
          o.timer = setTimeout(done, o.timeout);
        }

        o.observer.observe(el, config);

        return o;
      },

      /**
       * Adds an event listener.
       *
       * @param {DOMElement} el DOM element
       * @param {string} type Event name
       * @param {function} fn Callback function
       * @param {boolean|object} passiveOrOpts Passive mode or Options object
       *
       * @memberof BOOMR.utils
       */
      addListener: function(el, type, fn, passiveOrOpts) {
        var opts = false;

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("add_listener");
        /* END_DEBUG */

        if (el.addEventListener) {
          if (typeof passiveOrOpts === "object") {
            opts = passiveOrOpts;
          }
          else if (typeof passiveOrOpts === "boolean" && passiveOrOpts && BOOMR.browser.supportsPassive()) {
            opts = {
              capture: false,
              passive: true
            };
          }

          el.addEventListener(type, fn, opts);
        }
        else if (el.attachEvent) {
          el.attachEvent("on" + type, fn);
        }

        // ensure the type arry exists
        impl.listenerCallbacks[type] = impl.listenerCallbacks[type] || [];

        // save a reference to the target object and function
        impl.listenerCallbacks[type].push({ el: el, fn: fn});
      },

      /**
       * Removes an event listener.
       *
       * @param {DOMElement} el DOM element
       * @param {string} type Event name
       * @param {function} fn Callback function
       *
       * @memberof BOOMR.utils
       */
      removeListener: function(el, type, fn) {
        var i;

        /* BEGIN_DEBUG */
        BOOMR.utils.mark("remove_listener");
        /* END_DEBUG */

        if (el.removeEventListener) {
          // NOTE: We don't need to match any other options (e.g. passive)
          // from addEventListener, as removeEventListener only cares
          // about captive.
          el.removeEventListener(type, fn, false);
        }
        else if (el.detachEvent) {
          el.detachEvent("on" + type, fn);
        }

        if (impl.listenerCallbacks.hasOwnProperty(type)) {
          for (var i = 0; i < impl.listenerCallbacks[type].length; i++) {
            if (fn === impl.listenerCallbacks[type][i].fn &&
                el === impl.listenerCallbacks[type][i].el) {
              impl.listenerCallbacks[type].splice(i, 1);

              return;
            }
          }
        }
      },

      /**
       * Determines if the specified object is an `Array` or not
       *
       * @param {object} ary Object in question
       *
       * @returns {boolean} True if the object is an `Array`
       *
       * @memberof BOOMR.utils
       */
      isArray: function(ary) {
        return Object.prototype.toString.call(ary) === "[object Array]";
      },

      /**
       * Determines if the specified value is in the array
       *
       * @param {object} val Value to check
       * @param {object} ary Object in question
       *
       * @returns {boolean} True if the value is in the Array
       *
       * @memberof BOOMR.utils
       */
      inArray: function(val, ary) {
        var i;

        if (typeof val === "undefined" || typeof ary === "undefined" || !ary.length) {
          return false;
        }

        for (i = 0; i < ary.length; i++) {
          if (ary[i] === val) {
            return true;
          }
        }

        return false;
      },

      /**
       * Get a query parameter value from a URL's query string
       *
       * @param {string} param Query parameter name
       * @param {string|Object} [url] URL containing the query string, or a link object.
       * Defaults to `BOOMR.window.location`
       *
       * @returns {string|null} URI decoded value or null if param isn't a query parameter
       *
       * @memberof BOOMR.utils
       */
      getQueryParamValue: function(param, url) {
        var l, params, i, kv;

        if (!param) {
          return null;
        }

        if (typeof url === "string") {
          l = BOOMR.window.document.createElement("a");
          l.href = url;
        }
        else if (typeof url === "object" && typeof url.search === "string") {
          l = url;
        }
        else {
          l = BOOMR.window.location;
        }

        // Now that we match, pull out all query string parameters
        params = l.search.slice(1).split(/&/);

        for (i = 0; i < params.length; i++) {
          if (params[i]) {
            kv = params[i].split("=");

            if (kv.length && kv[0] === param) {
              try {
                return kv.length > 1 ? decodeURIComponent(kv.splice(1).join("=").replace(/\+/g, " ")) : "";
              }
              catch (e) {
                /**
                 * We have different messages for the same error in different browsers but
                 * we can look at the error name because it looks more consistent.
                 *
                 * Examples:
                 *  - URIError: The URI to be encoded contains invalid character (Edge)
                 *  - URIError: malformed URI sequence (Firefox)
                 *  - URIError: URI malformed (Chrome)
                 *  - URIError: URI error (Safari 13.0) / Missing on MDN but this is the result of my local tests.
                 *
                 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Malformed_URI#Message
                 */
                if (e && typeof e.name === "string" && e.name.indexOf("URIError") !== -1) {
                  // NOP
                }
                else {
                  throw e;
                }
              }
            }
          }
        }

        return null;
      },

      /**
       * Generates a pseudo-random UUID (Version 4):
       * https://en.wikipedia.org/wiki/Universally_unique_identifier
       *
       * @returns {string} UUID
       *
       * @memberof BOOMR.utils
       */
      generateUUID: function() {
        return "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g, function(c) {
          var r = Math.random() * 16 | 0;
          var v = c === "x" ? r : (r & 0x3 | 0x8);

          return v.toString(16);
        });
      },

      /**
       * Generates a random ID based on the specified number of characters.  Uses
       * characters a-z0-9.
       *
       * @param {number} chars Number of characters (max 40)
       *
       * @returns {string} Random ID
       *
       * @memberof BOOMR.utils
       */
      generateId: function(chars) {
        return "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx".substr(0, chars || 40).replace(/x/g, function(c) {
          var c = (Math.random() || 0.01).toString(36);

          // some implementations may return "0" for small numbers
          if (c === "0") {
            return "0";
          }
          else {
            return c.substr(2, 1);
          }
        });
      },

      /**
       * Attempt to serialize an object, preferring JSURL over JSON.stringify
       *
       * @param {Object} value Object to serialize
       * @returns {string} serialized version of value, empty-string if not possible
       */
      serializeForUrl: function(value) {
        if (BOOMR.utils.Compression && BOOMR.utils.Compression.jsUrl) {
          return BOOMR.utils.Compression.jsUrl(value);
        }

        if (window.JSON) {
          return JSON.stringify(value);
        }

        // not supported
        BOOMR.debug("JSON is not supported");

        return "";
      },

      /* BEGIN_DEBUG */
      /**
       * Attempt to deserialize an object, preferring JSURL over JSON.parse
       *
       * @param {string} value String to deserialize
       *
       * @returns {object|undefined} Deserialized version of value, undefined if not possible
       */
      deserializeForUrl: function(value) {
        if (BOOMR.utils.Compression && BOOMR.utils.Compression.jsUrlDecompress) {
          return BOOMR.utils.Compression.jsUrlDecompress(value);
        }

        if (window.JSON) {
          return JSON.parse(value);
        }

        // not supported
        BOOMR.debug("JSON is not supported");

        return;
      },
      /* END_DEBUG */

      /**
       * Attempt to identify the URL of boomerang itself using multiple methods for cross-browser support
       *
       * This method uses document.currentScript (which cannot be called from an event handler),
       * script.readyState (IE6-10),
       * and the stack property of a caught Error object.
       *
       * @returns {string} The URL of the currently executing boomerang script.
       */
      getMyURL: function() {
        var stack;
        // document.currentScript works in all browsers except for IE: https://caniuse.com/#feat=document-currentscript
        // #boomr-if-as works in all browsers if the page uses our standard iframe loader
        // #boomr-scr-as works in all browsers if the page uses our preloader loader
        // BOOMR_script will be undefined on IE for pages that do not use our standard loaders

        // Note that we do not use `w.document` or `d` here because we need the current execution context
        var BOOMR_script = (document.currentScript ||
          document.getElementById("boomr-if-as") ||
          document.getElementById("boomr-scr-as"));

        if (BOOMR_script) {
          return BOOMR_script.src;
        }

        // For IE 6-10 users on pages not using the standard loader, we iterate through all scripts backwards
        var scripts = document.getElementsByTagName("script"),
            i;

        // i-- is both a decrement as well as a condition, ie, the loop will terminate when i goes from 0 to -1
        for (i = scripts.length; i--;) {
          // We stop at the first script that has its readyState set to interactive indicating that it is
          // currently executing
          if (scripts[i].readyState === "interactive") {
            return scripts[i].src;
          }
        }

        // For IE 11, we throw an Error and inspect its stack property in the catch block
        // This also works on IE10, but throwing is disruptive so we try to avoid it and use
        // the less disruptive script iterator above
        try {
          throw new Error();
        }
        catch (e) {
          if ("stack" in e) {
            stack = this.arrayFilter(e.stack.split(/\n/), function(l) {
              return l.match(/https?:\/\//);
            });

            if (stack && stack.length) {
              return stack[0].replace(/.*(https?:\/\/.+?)(:\d+)+\D*$/m, "$1");
            }
          }
          // FWIW, on IE 8 & 9, the Error object does not contain a stack property, but if you have an uncaught error,
          // and a `window.onerror` handler (not using addEventListener), then the second argument to that handler is
          // the URL of the script that threw. The handler needs to `return true;` to prevent the default error handler
          // This flow is asynchronous though (due to the event handler), so won't work in a function return scenario
          // like this (we can't use promises because we would only need this hack in browsers that don't support
          // promises).
        }

        return "";
      },

      /*
       * Gets the Scroll x and y (rounded) for a page
       *
       * @returns {object} Scroll x and y coordinates
       */
      scroll: function() {
        // Adapted from:
        // https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollY
        var supportPageOffset = w.pageXOffset !== undefined;
        var isCSS1Compat = ((w.document.compatMode || "") === "CSS1Compat");

        var ret = {
          x: 0,
          y: 0
        };

        if (supportPageOffset) {
          if (typeof w.pageXOffset === "function") {
            ret.x = w.pageXOffset();
            ret.y = w.pageYOffset();
          }
          else {
            ret.x = w.pageXOffset;
            ret.y = w.pageYOffset;
          }
        }
        else if (isCSS1Compat) {
          ret.x = w.document.documentElement.scrollLeft;
          ret.y = w.document.documentElement.scrollTop;
        }
        else {
          ret.x = w.document.body.scrollLeft;
          ret.y = w.document.body.scrollTop;
        }

        // round to full numbers
        if (typeof ret.sx === "number") {
          ret.sx = Math.round(ret.sx);
        }

        if (typeof ret.sy === "number") {
          ret.sy = Math.round(ret.sy);
        }

        return ret;
      },

      /**
       * Gets the window height
       *
       * @returns {number} Window height
       */
      windowHeight: function() {
        return w.innerHeight || w.document.documentElement.clientHeight || w.document.body.clientHeight;
      },

      /**
       * Gets the window width
       *
       * @returns {number} Window width
       */
      windowWidth: function() {
        return w.innerWidth || w.document.documentElement.clientWidth || w.document.body.clientWidth;
      },

      /**
       * Determines if the function is native or not
       *
       * @param {function} fn Function
       *
       * @returns {boolean} True when the function is native
       */
      isNative: function(fn) {
        return !!fn &&
            fn.toString &&
            !fn.hasOwnProperty("toString") &&
            /\[native code\]/.test(String(fn));
      },

      /**
       * Overwrites a function on the specified object.
       *
       * When the Boomerang IFRAME unloads, it will swap the old
       * function back in, so calls to the functions are successful.
       *
       * If this isn't done, callers of the overwritten functions may still
       * call into freed Boomerang code or the IFRAME that is partially unloaded,
       * leading to "Freed script" errors or exceptions from accessing
       * unloaded DOM properties.
       *
       * This tracking isn't needed if Boomerang is loaded in the root
       * document, as everthing will be cleaned up along with Boomerang
       * on unload.
       *
       * @param {object} obj Object whose property will be overwritten
       * @param {string} functionName Function name
       * @param {function} newFn New function
       */
      overwriteNative: function(obj, functionName, newFn) {
        // bail if the object doesn't exist
        if (!obj || !newFn) {
          return;
        }

        // we only need to keep track if we're running Boomerang in
        // an IFRAME
        if (BOOMR.boomerang_frame !== BOOMR.window) {
          // note we overwrote this
          impl.nativeOverwrites.push({
            obj: obj,
            functionName: functionName,
            origFn: obj[functionName]
          });
        }

        obj[functionName] = newFn;
      },

      /**
       * Determines if the given input is an Integer.
       * Relies on standard Number.isInteger() function that available
       * is most browsers except IE. For IE, this relies on the polyfill
       * provided by MDN:
       * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger#Polyfill
       *
       * @param {number} input dat
       *
       * @returns {string} Random ID
       *
       * @memberof BOOMR.utils
       *
       */
      isInteger: function(data) {
        var isInt = Number.isInteger || function(value) {
          return typeof value === "number" &&
            isFinite(value) &&
            Math.floor(value) === value;
        };

        return isInt(data);
      },

      /**
       * Determines whether or not an Object is empty
       *
       * @param {object} data Data object
       *
       * @returns {boolean} True if the object has no properties
       */
      isObjectEmpty: function(data) {
        for (var propName in data) {
          if (data.hasOwnProperty(propName)) {
            return false;
          }
        }

        return true;
      },

      /**
       * Calculates the FNV hash of the specified string.
       *
       * @param {string} string Input string
       *
       * @returns {string} FNV hash of the input string
       *
       */
      hashString: function(string) {
        string = encodeURIComponent(string);
        var hval = 0x811c9dc5;

        for (var i = 0; i < string.length; i++) {
          hval = hval ^ string.charCodeAt(i);
          hval += (hval << 1) + (hval << 4) + (hval << 7) + (hval << 8) + (hval << 24);
        }

        var hash = (hval >>> 0).toString() + string.length;

        return parseInt(hash).toString(36);
      },

      /**
       * Wrapper of isUASameSiteNoneCompatible() that ensures that we pass correct User Agent string
       *
       * @returns {boolean} True if a browser can safely create SameSite=None cookie
       *
       * @memberof BOOMR.utils
       */
      isCurrentUASameSiteNoneCompatible: function() {
        if (w && w.navigator && !w.navigator.userAgentData) {
          if (w.navigator.userAgent && typeof w.navigator.userAgent === "string") {
            return this.isUASameSiteNoneCompatible(w.navigator.userAgent);
          }
        }

        return true;
      },

      /**
       * @param {string} uaString User agent string
       *
       * @returns {boolean} True if a browser can safely create SameSite=None cookie
       *
       * @memberof BOOMR.utils
       */
      isUASameSiteNoneCompatible: function(uaString) {
        /**
         * 1. UCBrowser lower than 12.13.2
         */
        var result = uaString.match(/(UCBrowser)\/(\d+\.\d+)\.(\d+)/);

        if (result) {
          var ucMajorMinorPart = parseFloat(result[2]);
          var ucPatch = result[3];

          if (ucMajorMinorPart === 12.13) {
            if (ucPatch <= 2) {
              return false;
            }

            return true;
          }

          if (ucMajorMinorPart < 12.13) {
            return false;
          }

          return true;
        }

        /**
         * 2. Chrome and Chromium version between 51 and 66
         *
         * This the regex covers both because a Chromium AU contains "Chromium/65.0.3325.181 Chrome/65.0.3325.181"
         */
        result = uaString.match(/(Chrome)\/(\d+)\.(\d+)\.(\d+)\.(\d+)/);

        if (result) {
          var chromeMajor = result[2];

          if (chromeMajor >= 51 && chromeMajor <= 66) {
            return false;
          }

          return true;
        }

        /**
         * 3. Mac OS 10.14.* check
         */
        result = uaString.match(/(Macintosh;.*Mac OS X 10_14[_\d]*.*) AppleWebKit\//);

        if (result) {
          // 3.2 Safari check
          result = uaString.match(/Version\/.* Safari\//);

          if (result) {
            // 3.2.1 Not Chrome based check
            result = uaString.match(/Chrom(?:e|ium)/);

            if (result === null) {
              return false;
            }
          }

          // 3.3 Mac OS embeded browser
          // eslint-disable-next-line max-len
          result = uaString.match(/^Mozilla\/\d+(?:\.\d+)* \(Macintosh;.*Mac OS X \d+(?:_\d+)*\) AppleWebKit\/\d+(?:\.\d+)* \(KHTML, like Gecko\)$/);

          if (result) {
            return false;
          }

          return true;
        }

        /**
         * 4. iOS and iPad OS 12 for all browsers
         */
        result = uaString.match(/(iP.+; CPU .*OS 12(?:_\d+)*.*)/);

        if (result) {
          return false;
        }

        return true;
      },

      /**
       * Given a HTML node, returns a Pseudo-CSS selector.
       *
       * Algorithm:
       * * Starting at the node itself, gather its selector: `elementName#elementId.elementClasses`
       *     * If the ID or classes are missing, skip them, e.g. just `elementName` or `elementName.elementClasses`
       * * Going up the parent tree via the `.parentNode`, stop at the first of:
       *     * The closest node (or itself) with an ID
       *     * The BODY node
       * * For each node found, prepend the node's selector to the full selector string
       * * Limit the number of selectors added to 5
       *     * If it takes more than 5 to get to an element with an ID or BODY, collapse to a `*` until they are reached
       *
       * For example:
       * * `<div> <span> <h1>` -> `div span h1`
       * * `<div id="test"> <span class="first">` -> `div#test span.first`
       * * `<span class="second"> <div id="test"> <span class="first">` -> `div#test span.first`
       * * `<span class="second"> <div id="test"> <span class="first second">` -> `div#test span.first.second`
       *
       * @param {Node} elementNode Node to generate a Pseudo-CSS selector for
       *
       * @return {string} Pseudo-CSS selector
       *
       * @memberof BOOMR.utils
       */
      makeSelector: function(elementNode) {
        var cssSelectors = [];
        var node = elementNode;

        // checks to see if a node is valid (element type, not null)
        // NOTE: Also sets the funtion-local `node` as the next node to iterate over
        function validateAndSetNode(nodeToCheck, isParent) {
          var isValid = true;

          // node invalid if null
          if (!nodeToCheck) {
            isValid = false;
          }

          // if node is not valid, see if there's a parent that is
          else {
            // nodeType 1 == Node.ELEMENT_NODE
            while (nodeToCheck && nodeToCheck.nodeType !== 1) {
              nodeToCheck = nodeToCheck.parentNode || nodeToCheck.parentElement;
            }

            // BODY is also invalid
            if (!nodeToCheck || nodeToCheck.tagName === "BODY") {
              isValid = false;
            }
          }

          //
          // If we're not just checking to see if a parent exists,
          // set node to the nearest valid parent if there is one.
          //
          // If node itself is valid, it will stay itself
          // (only changes if invalid but has a valid parent).
          if (!isParent) {
            node = nodeToCheck;
          }

          return isValid;
        }

        while (node) {
          // if node isn't null but is the wrong type, will set it to nearest valid parent
          var nodeIsValid = validateAndSetNode(node, false);

          if (!nodeIsValid || !node) {
            // if node is invalid and no valid parent, stop iterating
            break;
          }

          // add tagname and ID to selector if ID exists
          if (node.hasAttribute("id")) {
            var nodeId = node.tagName.toLowerCase() +
              "#" + node.getAttribute("id");

            cssSelectors.unshift(nodeId);

            // selector ends if an ID is found
            break;
          }

          // check if parent of this node is valid
          var parentIsValid = validateAndSetNode(node.parentNode, true);

          // if we don't have three tagnames in the selector yet,
          // or we do but this is the last valid one, add class if exists
          if (cssSelectors.length < 3 || (cssSelectors.length >= 3 && !parentIsValid)) {
            var nodeClass = node.tagName.toLowerCase();

            if (node.hasAttribute("class")) {
              nodeClass += "." + node.getAttribute("class").replace(/ +/g, ".");
            }

            cssSelectors.unshift(nodeClass);
          }
          // if > 3 tagnames in selector and parent is valid,
          // add an asterick if there is not one already
          else if (cssSelectors[0] !== "*") {
            cssSelectors.unshift("*");
          }

          // go to next node in sequence
          node = node.parentNode || node.parentElement;
        }

        // return CSS selector
        return cssSelectors.join(" ");
      }

      /* BEGIN_DEBUG */
      /**
       * DEBUG ONLY
       *
       * Loops over an array, running a function for each item
       *
       * @param {Array} array Array to iterate over
       * @param {function} fn Function to execute
       * @param {object} thisArg 'this' argument
       */
      , forEach: function(array, fn, thisArg) {
        if (!BOOMR.utils.isArray(array) || typeof fn !== "function") {
          return;
        }

        var length = array.length;

        for (var i = 0; i < length; i++) {
          if (array.hasOwnProperty(i)) {
            fn.call(thisArg, array[i], i, array);
          }
        }
      },

      /**
       * DEBUG ONLY
       *
       * Logs a UserTiming mark
       *
       * @param {string} name Mark name (prefixed by boomr:)
       */
      mark: function(name) {
        var p = BOOMR.getPerformance();

        if (p && typeof p.mark === "function" && !BOOMR.window.BOOMR_no_mark) {
          p.mark("boomr:" + name);
        }
      },

      /**
       * DEBUG ONLY
       *
       * Logs a UserTiming measure
       *
       * @param {string} name Mark name (prefixed by boomr:)
       */
      measure: function(measureName, startMarkName, endMarkName) {
        var p = BOOMR.getPerformance();

        if (p && typeof p.measure === "function" && !BOOMR.window.BOOMR_no_mark) {
          p.measure("boomr:" + measureName,
            startMarkName ? "boomr:" + startMarkName : undefined,
            endMarkName ? "boomr:" + endMarkName : undefined);
        }
      }
      /* END_DEBUG */

      // closes `utils`
    },

    /**
     * Browser feature detection flags.
     *
     * @class BOOMR.browser
     */
    browser: {
      results: {},

      /**
       * Whether or not the browser supports 'passive' mode for event
       * listeners
       *
       * @returns {boolean} True if the browser supports passive mode
       */
      supportsPassive: function() {
        if (typeof BOOMR.browser.results.supportsPassive === "undefined") {
          BOOMR.browser.results.supportsPassive = false;

          if (!Object.defineProperty) {
            return false;
          }

          try {
            var opts = Object.defineProperty({}, "passive", {
              get: function() {
                BOOMR.browser.results.supportsPassive = true;
              }
            });

            window.addEventListener("test", null, opts);
          }
          catch (e) {
            // NOP
          }
        }

        return BOOMR.browser.results.supportsPassive;
      }
    },

    /**
     * Initializes Boomerang by applying the specified configuration.
     *
     * All plugins' `init()` functions will be called with the same config as well.
     *
     * @param {object} config Configuration object
     * @param {boolean} [config.autorun] By default, boomerang runs automatically
     * and attaches its `page_ready` handler to the `window.onload` event.
     * If you set `autorun` to `false`, this will not happen and you will
     * need to call {@link BOOMR.page_ready} yourself.
     * @param {string} config.beacon_auth_key Beacon authorization key value
     * @param {string} config.beacon_auth_token Beacon authorization token.
     * @param {boolean} config.beacon_with_credentials Sends beacon with credentials
     * @param {boolean} config.beacon_disable_sendbeacon Disables `navigator.sendBeacon()` support
     * @param {string} config.beacon_url The URL to beacon results back to.
     * If not set, no beacon will be sent.
     * @param {boolean} config.beacon_url_force_https Forces protocol-relative Beacon URLs to HTTPS
     * @param {string} config.beacon_type `GET`, `POST` or `AUTO`
     * @param {string} [config.site_domain] The domain that all cookies should be set on
     * Boomerang will try to auto-detect this, but unless your site is of the
     * `foo.com` format, it will probably get it wrong. It's a good idea
     * to set this to whatever part of your domain you'd like to share
     * bandwidth and performance measurements across.
     * Set this to a falsy value to disable all cookies.
     * @param {boolean} [config.strip_query_string] Whether or not to strip query strings from all URLs
     *   (e.g. `u`, `pgu`, etc.)
     * @param {string} [config.user_ip] Despite its name, this is really a free-form
     * string used to uniquely identify the user's current internet
     * connection. It's used primarily by the bandwidth test to determine
     * whether it should re-measure the user's bandwidth or just use the
     * value stored in the cookie. You may use IPv4, IPv6 or anything else
     * that you think can be used to identify the user's network connection.
     * @param {string} [config.same_site_cookie] Used for creating cookies with `SameSite` with one
     *   of the following values: `None`, `Lax` or `Strict`.
     * @param {boolean} [config.secure_cookie] When `true` all cookies will be created with `Secure` flag.
     * @param {boolean} [config.request_client_hints] When `true`, gather high entropy values for Architecture,
     * Model and Platform data from navigator.userAgentData.
     * @param {boolean} [config.no_unload] Disables all unload handlers and the Unload beacons
     * @param {function} [config.log] Logger to use. Set to `null` to disable logging.
     * @param {function} [<plugins>] Each plugin has its own section
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    init: function(config) {
      var i, k,
          properties = [
            "autorun",
            "beacon_auth_key",
            "beacon_auth_token",
            "beacon_with_credentials",
            "beacon_disable_sendbeacon",
            "beacon_url",
            "beacon_url_force_https",
            "beacon_type",
            "site_domain",
            "strip_query_string",
            "user_ip",
            "same_site_cookie",
            "secure_cookie",
            "request_client_hints",
            "no_unload"
          ];

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("init:start");
      /* END_DEBUG */

      BOOMR_check_doc_domain();

      if (!config) {
        config = {};
      }

      // ensure logging is setup properly (or null'd out for production)
      if (config.log !== undefined) {
        this.log = config.log;
      }

      if (!this.log) {
        this.log = function() {};
      }

      if (!this.pageId) {
        // generate a random page ID for this page's lifetime
        this.pageId = BOOMR.utils.generateId(8);
        BOOMR.debug("Generated PageID: " + this.pageId);
      }

      if (config.primary && impl.handlers_attached) {
        return this;
      }

      if (typeof config.site_domain !== "undefined") {
        if (/:/.test(config.site_domain)) {
          // domains with : are not valid, fall back to the current hostname
          config.site_domain = w.location.hostname.toLowerCase();
        }

        this.session.domain = config.site_domain;
      }

      if (BOOMR.session.enabled && typeof BOOMR.session.ID === "undefined") {
        BOOMR.session.ID = BOOMR.utils.generateUUID();
      }

      // Set autorun if in config right now, as plugins that listen for page_ready
      // event may fire when they .init() if onload has already fired, and whether
      // or not we should fire page_ready depends on config.autorun.
      if (typeof config.autorun !== "undefined") {
        impl.autorun = config.autorun;
      }

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("init:plugins:start");
      /* END_DEBUG */

      for (k in this.plugins) {
        if (this.plugins.hasOwnProperty(k)) {
          // config[plugin].enabled has been set to false
          if (config[k] &&
              config[k].hasOwnProperty("enabled") &&
              config[k].enabled === false) {
            impl.disabled_plugins[k] = 1;

            if (typeof this.plugins[k].disable === "function") {
              this.plugins[k].disable();
            }

            continue;
          }

          // plugin was previously disabled
          if (impl.disabled_plugins[k]) {
            // and has not been explicitly re-enabled
            if (!config[k] ||
                !config[k].hasOwnProperty("enabled") ||
                config[k].enabled !== true) {
              continue;
            }

            if (typeof this.plugins[k].enable === "function") {
              this.plugins[k].enable();
            }

            // plugin is now enabled
            delete impl.disabled_plugins[k];
          }

          // plugin exists and has an init method
          if (typeof this.plugins[k].init === "function") {
            try {
              /* BEGIN_DEBUG */
              BOOMR.utils.mark("init:plugins:" + k + ":start");
              /* END_DEBUG */

              this.plugins[k].init(config);

              /* BEGIN_DEBUG */
              BOOMR.utils.mark("init:plugins:" + k + ":end");
              BOOMR.utils.measure(
                "init:plugins:" + k,
                "init:plugins:" + k + ":start",
                "init:plugins:" + k + ":end");
              /* END_DEBUG */
            }
            catch (err) {
              BOOMR.addError(err, k + ".init");
            }
          }
        }
      }

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("init:plugins:end");
      BOOMR.utils.measure(
        "init:plugins",
        "init:plugins:start",
        "init:plugins:end");
      /* END_DEBUG */

      for (i = 0; i < properties.length; i++) {
        if (config[properties[i]] !== undefined) {
          impl[properties[i]] = config[properties[i]];
        }
      }

      // if client hints are requested, then squirrel away user agent data of architecture, model, and platform
      // version on impl for later use on the beacon
      if (impl.request_client_hints === true &&
        w && w.navigator && w.navigator.userAgentData &&
        typeof w.navigator.userAgentData.getHighEntropyValues === "function") {
        w.navigator.userAgentData.getHighEntropyValues(["architecture", "model", "platformVersion"]).then(function(ua) {
          impl.userAgentData = ua;
        });
      }

      // if it's the first call to init (handlers aren't attached) and we're not asked to wait OR
      // it's the second init call (handlers are attached) and we were previously waiting
      // then we set up the page ready autorun functionality
      if ((!impl.handlers_attached && !config.wait) || (impl.handlers_attached && impl.waiting_for_config)) {
        // The developer can override onload by setting autorun to false
        if (!impl.onloadfired && (impl.autorun === undefined || impl.autorun !== false)) {
          if (BOOMR.hasBrowserOnloadFired()) {
            BOOMR.loadedLate = true;
          }

          BOOMR.attach_page_ready(BOOMR.page_ready_autorun);
        }

        impl.waiting_for_config = false;
      }

      // only attach handlers once
      if (impl.handlers_attached) {
        /* BEGIN_DEBUG */
        BOOMR.utils.mark("init:end");
        BOOMR.utils.measure(
          "init",
          "init:start",
          "init:end");
        /* END_DEBUG */

        return this;
      }

      if (config.wait) {
        impl.waiting_for_config = true;
      }

      BOOMR.attach_page_ready(function() {
        // if we're not using the loader snippet, save the onload time for
        // browsers that do not support NavigationTiming.
        // This will be later than onload if boomerang arrives late on the
        // page but it's the best we can do
        if (!BOOMR.t_onload) {
          BOOMR.t_onload = BOOMR.now();
        }
      });

      BOOMR.utils.addListener(w, "DOMContentLoaded", function() {
        impl.fireEvent("dom_loaded");
      });

      BOOMR.fireEvent("config", config);
      BOOMR.subscribe("config", function(beaconConfig) {
        if (beaconConfig.beacon_url) {
          impl.beacon_url = beaconConfig.beacon_url;
        }
      });

      BOOMR.subscribe("spa_navigation", impl.spaNavigation, null, impl);

      (function() {
        var forms, iterator;

        if (visibilityChange !== undefined) {
          BOOMR.utils.addListener(d, visibilityChange, function() {
            impl.fireEvent("visibility_changed");
          });

          // save the current visibility state
          impl.lastVisibilityState = BOOMR.visibilityState();

          BOOMR.subscribe("visibility_changed", function() {
            var visState = BOOMR.visibilityState();

            // record the last time each visibility state occurred
            BOOMR.lastVisibilityEvent[visState] = BOOMR.now();
            BOOMR.debug("Visibility changed from " + impl.lastVisibilityState + " to " + visState);

            // if we transitioned from prerender to hidden or visible, fire the prerender_to_visible event
            if (impl.lastVisibilityState === "prerender" &&
                visState !== "prerender") {
              // note that we transitioned from prerender on the beacon for debugging
              BOOMR.addVar("vis.pre", "1");

              // let all listeners know
              impl.fireEvent("prerender_to_visible");
            }

            impl.lastVisibilityState = visState;
          });
        }

        BOOMR.utils.addListener(d, "mouseup", impl.xb_handler("click"));

        forms = d.getElementsByTagName("form");
        for (iterator = 0; iterator < forms.length; iterator++) {
          BOOMR.utils.addListener(forms[iterator], "submit", impl.xb_handler("form_submit"));
        }

        if (!w.onpagehide && w.onpagehide !== null) {
          // This must be the last one to fire
          // We only clear w on browsers that don't support onpagehide because
          // those that do are new enough to not have memory leak problems of
          // some older browsers
          BOOMR.utils.addListener(w, "unload", function() {
            BOOMR.window = w = null;
          });
        }

        // if we were loaded in an IFRAME, try to keep track if the IFRAME was unloaded
        if (BOOMR.boomerang_frame !== BOOMR.window) {
          BOOMR.utils.addListener(BOOMR.boomerang_frame, "unload", impl.onFrameUnloaded);
        }
      }());

      impl.handlers_attached = true;

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("init:end");
      BOOMR.utils.measure(
        "init",
        "init:start",
        "init:end");
      /* END_DEBUG */

      return this;
    },

    /**
     * Attach a callback to the `pageshow` or `onload` event if `onload` has not
     * been fired otherwise queue it to run immediately
     *
     * @param {function} cb Callback to run when `onload` fires or page is visible (`pageshow`)
     *
     * @memberof BOOMR
     */
    attach_page_ready: function(cb) {
      if (BOOMR.hasBrowserOnloadFired()) {
        this.setImmediate(cb, null, null, BOOMR);
      }
      else {
        // Use `pageshow` if available since it will fire even if page came from a back-forward page cache.
        // Browsers that support `pageshow` will not fire `onload` if navigation was through a back/forward button
        // and the page was retrieved from back-forward cache.
        if (w.onpagehide || w.onpagehide === null) {
          BOOMR.utils.addListener(w, "pageshow", cb);
        }
        else {
          BOOMR.utils.addListener(w, "load", cb);
        }
      }
    },

    /**
     * Sends the `page_ready` event only if `autorun` is still true after
     * {@link BOOMR.init} is called.
     *
     * @param {Event} ev Event
     *
     * @memberof BOOMR
     */
    page_ready_autorun: function(ev) {
      if (impl.autorun) {
        BOOMR.page_ready(ev, true);
      }
    },

    /**
     * Method that fires the {@link BOOMR#event:page_ready} event. Call this
     * only if you've set `autorun` to `false` when calling the {@link BOOMR.init}
     * method. You should call this method when you determine that your page
     * is ready to be used by your user. This will be the end-time used in
     * the page load time measurement. Optionally, you can pass a Unix Epoch
     * timestamp as a parameter or set the global `BOOMR_page_ready` var that will
     * be used as the end-time instead.
     *
     * @param {Event|number} [ev] Ready event or optional load event end timestamp if called manually
     * @param {boolean} auto True if called by `page_ready_autorun`
     *
     * @returns {BOOMR} Boomerang object
     *
     * @example
     * BOOMR.init({ autorun: false, ... });
     * // wait until the page is ready, i.e. your view has loaded
     * BOOMR.page_ready();
     *
     * @memberof BOOMR
     */
    page_ready: function(ev, auto) {
      var tm_page_ready;

      // a number can be passed as the first argument if called manually which
      // will be used as the loadEventEnd time
      if (!auto && typeof ev === "number") {
        tm_page_ready = ev;
        ev = null;
      }

      if (!ev) {
        ev = w.event;
      }

      if (!ev) {
        ev = {
          name: "load"
        };
      }

      // if we were called manually or global BOOMR_page_ready was set then
      // add loadEventEnd and note this was 'pr' on the beacon
      if (!auto) {
        ev.timing = ev.timing || {};

        // use timestamp parameter or global BOOMR_page_ready if set, otherwise use
        // the current timestamp
        if (tm_page_ready) {
          ev.timing.loadEventEnd = tm_page_ready;
        }
        else if (typeof w.BOOMR_page_ready === "number") {
          ev.timing.loadEventEnd = w.BOOMR_page_ready;
        }
        else {
          ev.timing.loadEventEnd = BOOMR.now();
        }

        BOOMR.addVar("pr", 1, true);
      }
      else if (typeof w.BOOMR_page_ready === "number") {
        ev.timing = ev.timing || {};
        // the global BOOMR_page_ready will override our loadEventEnd
        ev.timing.loadEventEnd = w.BOOMR_page_ready;

        BOOMR.addVar("pr", 1, true);
      }

      if (impl.onloadfired) {
        return this;
      }

      impl.fireEvent("page_ready", ev);
      impl.onloadfired = true;

      return this;
    },

    /**
     * Determines whether or not the page's `onload` event has fired
     *
     * @returns {boolean} True if page's onload was called
     */
    hasBrowserOnloadFired: function() {
      var p = BOOMR.getPerformance();
      // if the document is `complete` then the `onload` event has already occurred, we'll fire the callback
      // immediately.
      //
      // When `document.write` is used to replace the contents of the page and inject boomerang, the document
      // `readyState` will go from `complete` back to `loading` and then to `complete` again. The second transition
      // to `complete` doesn't fire a second `pageshow` event in some browsers (e.g. Safari). We need to check if
      // `performance.timing.loadEventStart` or `BOOMR_onload` has occurred to detect this scenario. Will not work for
      // older Safari that doesn't have NavTiming

      return ((d.readyState && d.readyState === "complete") ||
          (p && p.timing && p.timing.loadEventStart > 0) ||
          w.BOOMR_onload > 0);
    },

    /**
     * Determines whether or not the page's `onload` event has fired, or
     * if `autorun` is false, whether {@link BOOMR.page_ready} was called.
     *
     * @returns {boolean} True if `onload` or {@link BOOMR.page_ready} were called
     *
     * @memberof BOOMR
     */
    onloadFired: function() {
      return impl.onloadfired;
    },

    /**
     * The callback function may return a falsy value to disconnect the observer
     * after it returns, or a truthy value to keep watching for mutations. If
     * the return value is numeric and greater than 0, then this will be the new timeout.
     * If it is boolean instead, then the timeout will not fire any more so
     * the caller MUST call disconnect() at some point
     *
     * @callback BOOMR~setImmediateCallback
     * @param {object} data The passed in `data` object
     * @param {object} cb_data The passed in `cb_data` object
     * @param {Error} callstack An Error object that holds the callstack for
     * when `setImmediate` was called, used to determine what called the callback
     */

    /**
     * Defer the function `fn` until the next instant the browser is free from
     * user tasks.
     *
     * @param {BOOMR~setImmediateCallback} fn The callback function.
     * @param {object} [data] Any data to pass to the callback function
     * @param {object} [cb_data] Any passthrough data for the callback function.
     * This differs from `data` when `setImmediate` is called via an event
     * handler and `data` is the Event object
     * @param {object} [cb_scope] The scope of the callback function if it is a method of an object
     *
     * @returns nothing
     *
     * @memberof BOOMR
     */
    setImmediate: function(fn, data, cb_data, cb_scope) {
      var cb, cstack;

      /* BEGIN_DEBUG */
      // DEBUG: This is to help debugging, we'll see where setImmediate calls were made from
      if (typeof Error !== "undefined") {
        cstack = new Error();
        cstack = cstack.stack ? cstack.stack.replace(/^Error/, "Called") : undefined;
      }
      /* END_DEBUG */

      cb = function() {
        fn.call(cb_scope || null, data, cb_data || {}, cstack);
        cb = null;
      };

      if (w.requestIdleCallback) {
        // set a timeout since rIC doesn't get called reliably in chrome headless
        w.requestIdleCallback(cb, {timeout: 1000});
      }
      else if (w.setImmediate) {
        w.setImmediate(cb);
      }
      else {
        setTimeout(cb, 10);
      }
    },

    /**
     * Gets the current time in milliseconds since the Unix Epoch (Jan 1 1970).
     *
     * In browsers that support `DOMHighResTimeStamp`, this will be replaced
     * by a function that adds `performance.now()` to `navigationStart`
     * (with milliseconds.microseconds resolution).
     *
     * @function
     *
     * @returns {TimeStamp} Milliseconds since Unix Epoch
     *
     * @memberof BOOMR
     */
    now: (function() {
      return Date.now || function() {
        return new Date().getTime();
      };
    }()),

    /**
     * Gets the `window.performance` object of the root window.
     *
     * Checks vendor prefixes for older browsers (e.g. IE9).
     *
     * @returns {Performance|undefined} `window.performance` if it exists
     *
     * @memberof BOOMR
     */
    getPerformance: function() {
      try {
        if (BOOMR.window) {
          if ("performance" in BOOMR.window && BOOMR.window.performance) {
            return BOOMR.window.performance;
          }

          // vendor-prefixed fallbacks
          return BOOMR.window.msPerformance ||
              BOOMR.window.webkitPerformance ||
              BOOMR.window.mozPerformance;
        }
      }
      catch (ignore) {
        // empty
      }
    },

    /**
     * Allows us to force SameSite=None from a Boomerang plugin or a third party code.
     *
     * When this function is called then Boomerang won't honor "same_site_cookie"
     * configuration key and won't attempt to return the default value of SameSite=Lax .
     *
     * @memberof BOOMR
     */
    forceSameSiteCookieNone: function() {
      impl.forced_same_site_cookie_none = true;
    },

    /**
     * Get high resolution delta timestamp from time origin
     *
     * This function needs to approximate the time since the performance timeOrigin
     * or Navigation Timing API's `navigationStart` time.
     * If available, `performance.now()` can provide this value.
     * If not we either get the navigation start time from the RT plugin or
     * from `t_lstart` or `t_start`. Those values are subtracted from the current
     * time to derive a time since `navigationStart` value.
     *
     * @returns {float} Exact or approximate time since the time origin.
     */
    hrNow: function() {
      var now, navigationStart,
          p = BOOMR.getPerformance();

      if (p && p.now) {
        now = p.now();
      }
      else {
        navigationStart = (BOOMR.plugins.RT && BOOMR.plugins.RT.navigationStart &&
          BOOMR.plugins.RT.navigationStart()) || BOOMR.t_lstart || BOOMR.t_start;

        // if navigationStart is undefined, we'll be returning NaN
        now = BOOMR.now() - navigationStart;
      }

      return now;
    },

    /**
     * Gets the `document.visibilityState`, or `visible` if Page Visibility
     * is not supported.
     *
     * @function
     *
     * @returns {string} Visibility state
     *
     * @memberof BOOMR
     */
    visibilityState: (visibilityState === undefined ? function() {
      return "visible";
    } : function() {
      return d[visibilityState];
    }),

    /**
     * An mapping of visibliity event states to the latest time they happened
     *
     * @type {object}
     *
     * @memberof BOOMR
     */
    lastVisibilityEvent: {},

    /**
     * Registers a Boomerang event.
     *
     * @param {string} e_name Event name
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    registerEvent: function(e_name) {
      if (impl.events.hasOwnProperty(e_name)) {
        // already registered
        return this;
      }

      // create a new queue of handlers
      impl.events[e_name] = [];

      return this;
    },

    /**
     * Disables boomerang from doing anything further:
     * 1. Clears event handlers (such as onload)
     * 2. Clears all event listeners
     *
     * @memberof BOOMR
     */
    disable: function() {
      impl.clearEvents();
      impl.clearListeners();
    },

    /**
     * Fires a Boomerang event
     *
     * @param {string} e_name Event name
     * @param {object} data Event payload
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    fireEvent: function(e_name, data) {
      return impl.fireEvent(e_name, data);
    },

    /**
     * @callback BOOMR~subscribeCallback
     * @param {object} eventData Event data
     * @param {object} cb_data Callback data
     */

    /**
     * Subscribes to a Boomerang event
     *
     * @param {string} e_name Event name, i.e. {@link BOOMR#event:page_ready}.
     * @param {BOOMR~subscribeCallback} fn Callback function
     * @param {object} cb_data Callback data, passed as the second parameter to the callback function
     * @param {object} cb_scope Callback scope.  If set to an object, then the
     * callback function is called as a method of this object, and all
     * references to `this` within the callback function will refer to `cb_scope`.
     * @param {boolean} once Whether or not this callback should only be run once
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    subscribe: function(e_name, fn, cb_data, cb_scope, once) {
      var i, handler, ev;

      e_name = e_name.toLowerCase();

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("subscribe");
      BOOMR.utils.mark("subscribe:" + e_name);
      /* END_DEBUG */

      // translate old names
      if (impl.translate_events[e_name]) {
        e_name = impl.translate_events[e_name];
      }

      if (!impl.events.hasOwnProperty(e_name)) {
        // allow subscriptions before they're registered
        impl.events[e_name] = [];
      }

      ev = impl.events[e_name];

      // don't allow a handler to be attached more than once to the same event
      for (i = 0; i < ev.length; i++) {
        handler = ev[i];

        if (handler && handler.fn === fn && handler.cb_data === cb_data && handler.scope === cb_scope) {
          return this;
        }
      }

      ev.push({
        fn: fn,
        cb_data: cb_data || {},
        scope: cb_scope || null,
        once: once || false
      });

      // attaching to page_ready after onload fires, so call soon
      if (e_name === "page_ready" && impl.onloadfired && impl.autorun) {
        this.setImmediate(fn, null, cb_data, cb_scope);
      }

      // Note: If no_unload is set, don't listen to any unload-style events.
      if (!impl.no_unload && (e_name === "page_unload" || e_name === "before_unload")) {
        // Keep track of how many pagehide/unload/beforeunload handlers we're registering
        impl.unloadEventsCount++;

        (function() {
          var unloadHandler = function boomerangUnloadHandler(evt) {
            if (impl.no_unload) {
              // may have been set after the initial load
              return;
            }

            if (fn) {
              fn.call(cb_scope, evt || w.event, cb_data);
            }

            // clear so this doesn't run twice
            fn = null;

            // If this was the last pagehide/unload/beforeunload handler,
            // we'll try to send the beacon immediately after it is done.
            // The beacon will only be sent if one of the handlers has queued it.
            if (++impl.unloadEventCalled === impl.unloadEventsCount) {
              BOOMR.real_sendBeacon();
            }
          };

          //
          // For modern browsers that support pagehide, listen to that event,
          // and do not listen to beforeunload/unload as they can break BFCache navigations.
          //
          if (w.onpagehide || w.onpagehide === null) {
            BOOMR.utils.addListener(w, "pagehide", unloadHandler);
          }
          else {
            //
            // For before_unload event in older browsers, attach handlers directly
            // to the unload and beforeunload events. Not all older browsers support
            // beforeunload. The first of the two to fire will clear so that the
            // second doesn't fire.
            //
            if (e_name === "page_unload") {
              BOOMR.utils.addListener(w, "unload", unloadHandler);
            }

            BOOMR.utils.addListener(w, "beforeunload", unloadHandler);
          }
        }());
      }

      return this;
    },

    /**
     * Logs an internal Boomerang error.
     *
     * If the {@link BOOMR.plugins.Errors} plugin is enabled, this data will
     * be compressed on the `err` beacon parameter.  If not, it will be included
     * in uncompressed form on the `errors` parameter.
     *
     * @param {string|object} err Error
     * @param {string} [src] Source
     * @param {object} [extra] Extra data
     *
     * @memberof BOOMR
     */
    addError: function BOOMR_addError(err, src, extra) {
      var str,
          E = BOOMR.plugins.Errors;

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("add_error");
      /* END_DEBUG */

      BOOMR.error("Boomerang caught error: " + err + ", src: " + src + ", extra: " + extra);

      //
      // Use the Errors plugin if it's enabled
      //
      if (E && E.is_supported()) {
        if (typeof err === "string") {
          E.send({
            message: err,
            extra: extra,
            functionName: src,
            noStack: true
          }, E.VIA_APP, E.SOURCE_BOOMERANG);
        }
        else {
          if (typeof src === "string") {
            err.functionName = src;
          }

          if (typeof extra !== "undefined") {
            err.extra = extra;
          }

          E.send(err, E.VIA_APP, E.SOURCE_BOOMERANG);
        }

        return;
      }

      if (typeof err !== "string") {
        str = String(err);

        if (str.match(/^\[object/)) {
          str = err.name + ": " + (err.description || err.message).replace(/\r\n$/, "");
        }

        err = str;
      }

      if (src !== undefined) {
        err = "[" + src + ":" + BOOMR.now() + "] " + err;
      }

      if (extra) {
        err += ":: " + extra;
      }

      if (impl.errors[err]) {
        impl.errors[err]++;
      }
      else {
        impl.errors[err] = 1;
      }
    },

    /**
     * Determines if the specified Error is a Cross-Origin error.
     *
     * @param {string|object} err Error
     *
     * @returns {boolean} True if the Error is a Cross-Origin error.
     *
     * @memberof BOOMR
     */
    isCrossOriginError: function(err) {
      // These are expected for cross-origin iframe access.
      // For IE and Edge, we'll also check the error number for non-English browsers
      return err.name === "SecurityError" ||
        (err.name === "TypeError" && err.message === "Permission denied") ||
        (err.name === "Error" && err.message && err.message.match(/^(Permission|Access is) denied/)) ||
        // IE/Edge error number for "Permission Denied"
        err.number === -2146828218;
    },

    /**
     * Add one or more parameters to the beacon.
     *
     * This method may either be called with a single object containing
     * key/value pairs, or with two parameters, the first is the variable
     * name and the second is its value.
     *
     * All names should be strings usable in a URL's query string.
     *
     * We recommend only using alphanumeric characters and underscores, but you
     * can use anything you like.
     *
     * Values should be strings (or numbers), and have the same restrictions
     * as names.
     *
     * Parameters will be on all subsequent beacons unless `singleBeacon` is
     * set. Early beacons will not clear vars that were set with `singleBeacon`.
     *
     * @param {string|object} name Variable name
     * @param {string|object} [val] Value.  If the first parameter is an object, this
     * becomes the singleBeacon parameter.
     * @param {boolean} [singleBeacon=false] Whether or not to add to a single beacon
     * or all beacons.
     *
     * @returns {BOOMR} Boomerang object
     *
     * @example
     * BOOMR.addVar("page_id", 123);
     * BOOMR.addVar({"page_id": 123, "user_id": "Person1"});
     *
     * @memberof BOOMR
     */
    addVar: function(name, value, singleBeacon) {
      /* BEGIN_DEBUG */
      BOOMR.utils.mark("add_var");
      /* END_DEBUG */

      if (typeof name === "string") {
        impl.vars[name] = value;

        if (singleBeacon) {
          impl.singleBeaconVars[name] = 1;
        }
      }
      else if (typeof name === "object") {
        var o = name,
            k;

        for (k in o) {
          if (o.hasOwnProperty(k)) {
            impl.vars[k] = o[k];

            // For object-set, the second parameter (or third) can be
            // true to force singleBeacon.  If so, remove this
            // after the first beacon
            if (value || singleBeacon) {
              impl.singleBeaconVars[k] = 1;
            }
          }
        }
      }

      return this;
    },

    /**
     * Appends data to a beacon.
     *
     * If the value already exists, a comma is added and the new data is applied.
     *
     * @param {string} name Variable name
     * @param {string} val Value
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    appendVar: function(name, value) {
      var existing = BOOMR.getVar(name) || "";

      if (existing) {
        existing += ",";
      }

      BOOMR.addVar(name, existing + value);

      return this;
    },

    /**
     * Removes one or more variables from the beacon URL. This is useful within
     * a plugin to reset the values of parameters that it is about to set.
     *
     * Plugins can also use this in the {@link BOOMR#event:beacon} event to clear
     * any variables that should only live on a single beacon.
     *
     * This method accepts either a list of variable names, or a single
     * array containing a list of variable names.
     *
     * @param {string[]|string} name Variable name or list
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    removeVar: function(arg0) {
      var i, params;

      if (!arguments.length) {
        return this;
      }

      if (arguments.length === 1 && BOOMR.utils.isArray(arg0)) {
        params = arg0;
      }
      else {
        params = arguments;
      }

      for (i = 0; i < params.length; i++) {
        if (impl.vars.hasOwnProperty(params[i])) {
          delete impl.vars[params[i]];
        }
      }

      return this;
    },

    /**
     * Determines whether or not the beacon has the specified variable.
     *
     * @param {string} name Variable name
     *
     * @returns {boolean} True if the variable is set.
     *
     * @memberof BOOMR
     */
    hasVar: function(name) {
      return impl.vars.hasOwnProperty(name);
    },

    /**
     * Gets the specified variable.
     *
     * @param {string} name Variable name
     *
     * @returns {object|undefined} Variable, or undefined if it isn't set
     *
     * @memberof BOOMR
     */
    getVar: function(name) {
      return impl.vars[name];
    },

    /**
     * Sets a variable's priority in the beacon URL.
     * -1 = beginning of the URL
     * 0  = middle of the URL (default)
     * 1  = end of the URL
     *
     * @param {string} name Variable name
     * @param {number} pri Priority (-1 or 1)
     *
     * @returns {BOOMR} Boomerang object
     *
     * @memberof BOOMR
     */
    setVarPriority: function(name, pri) {
      if (typeof pri !== "number" || Math.abs(pri) !== 1) {
        return this;
      }

      impl.varPriority[pri][name] = 1;

      return this;
    },

    /**
     * Sets the Referrers variable.
     *
     * @param {string} r Referrer from the document.referrer
     *
     * @memberof BOOMR
     */
    setReferrer: function(r) {
      // document.referrer
      impl.r = r;
    },

    /**
     * Starts a timer for a dynamic request.
     *
     * Once the named request has completed, call `loaded()` to send a beacon
     * with the duration.
     *
     * @example
     * var timer = BOOMR.requestStart("my-timer");
     * // do stuff
     * timer.loaded();
     *
     * @param {string} name Timer name
     *
     * @returns {object} An object with a `.loaded()` function that you can call
     *     when the dynamic timer is complete.
     *
     * @memberof BOOMR
     */
    requestStart: function(name) {
      var t_start = BOOMR.now();

      BOOMR.plugins.RT.startTimer("xhr_" + name, t_start);

      return {
        loaded: function(data) {
          BOOMR.responseEnd(name, t_start, data);
        }
      };
    },

    /**
     * Determines if Boomerang can send a beacon.
     *
     * Queryies all plugins to see if they implement `readyToSend()`,
     * and if so, that they return `true`.
     *
     * If not, the beacon cannot be sent.
     *
     * @returns {boolean} True if Boomerang can send a beacon
     *
     * @memberof BOOMR
     */
    readyToSend: function() {
      var plugin;

      for (plugin in this.plugins) {
        if (this.plugins.hasOwnProperty(plugin)) {
          if (impl.disabled_plugins[plugin]) {
            continue;
          }

          if (typeof this.plugins[plugin].readyToSend === "function" &&
              this.plugins[plugin].readyToSend() === false) {
            BOOMR.debug("Plugin " + plugin + " is not ready to send");

            return false;
          }
        }
      }

      return true;
    },

    /**
     * Sends a beacon for a dynamic request.
     *
     * @param {string|object} name Timer name or timer object data.
     * @param {string} [name.initiator] Initiator, such as `xhr` or `spa`
     * @param {string} [name.url] URL of the request
     * @param {TimeStamp} t_start Start time
     * @param {object} data Request data
     * @param {TimeStamp} t_end End time
     *
     * @memberof BOOMR
     */
    responseEnd: function(name, t_start, data, t_end) {
      // take the now timestamp for start and end, if unspecified, in case we delay this beacon
      t_start = typeof t_start === "number" ? t_start : BOOMR.now();
      t_end = typeof t_end === "number" ? t_end : BOOMR.now();

      // wait until all plugins are ready to send
      if (!BOOMR.readyToSend()) {
        BOOMR.debug("Attempted to call responseEnd before all plugins were Ready to Send, trying again...");

        // try again later
        setTimeout(function() {
          BOOMR.responseEnd(name, t_start, data, t_end);
        }, 1000);

        return;
      }

      // Wait until we've sent the Page Load beacon first
      if (!BOOMR.hasSentPageLoadBeacon() &&
          !BOOMR.utils.inArray(name.initiator, BOOMR.constants.BEACON_TYPE_SPAS)) {
        // wait for a beacon, then try again
        BOOMR.subscribe("page_load_beacon", function() {
          BOOMR.responseEnd(name, t_start, data, t_end);
        }, null, BOOMR, true);

        return;
      }

      // Ensure we don't have two beacons trying to send data at the same time
      if (impl.beaconInQueue) {
        // wait until the beacon is sent, then try again
        BOOMR.subscribe("beacon", function() {
          BOOMR.responseEnd(name, t_start, data, t_end);
        }, null, BOOMR, true);

        return;
      }

      // Lock the beacon queue
      impl.beaconInQueue = true;

      if (typeof name === "object") {
        if (!name.url) {
          BOOMR.debug("BOOMR.responseEnd: First argument must have a url property if it's an object");

          return;
        }

        impl.fireEvent("xhr_load", name);
      }
      else {
        // flush out any queue'd beacons before we set the Page Group
        // and timers
        BOOMR.real_sendBeacon();

        BOOMR.addVar("xhr.pg", name, true);

        BOOMR.plugins.RT.startTimer("xhr_" + name, t_start);

        impl.fireEvent("xhr_load", {
          name: "xhr_" + name,
          data: data,
          timing: {
            loadEventEnd: t_end
          }
        });
      }
    },

    //
    // uninstrumentXHR, instrumentXHR, uninstrumentFetch and instrumentFetch
    // are stubs that will be replaced by auto-xhr.js if active.
    //
    /**
     * Undo XMLHttpRequest instrumentation and reset the original `XMLHttpRequest`
     * object
     *
     * This is implemented in `plugins/auto-xhr.js` {@link BOOMR.plugins.AutoXHR}.
     *
     * @memberof BOOMR
     */
    uninstrumentXHR: function() { },

    /**
     * Instrument all requests made via XMLHttpRequest to send beacons.
     *
     * This is implemented in `plugins/auto-xhr.js` {@link BOOMR.plugins.AutoXHR}.
     *
     * @memberof BOOMR
     */
    instrumentXHR: function() { },

    /**
     * Undo fetch instrumentation and reset the original `fetch`
     * function
     *
     * This is implemented in `plugins/auto-xhr.js` {@link BOOMR.plugins.AutoXHR}.
     *
     * @memberof BOOMR
     */
    uninstrumentFetch: function() { },

    /**
     * Instrument all requests made via fetch to send beacons.
     *
     * This is implemented in `plugins/auto-xhr.js` {@link BOOMR.plugins.AutoXHR}.
     *
     * @memberof BOOMR
     */
    instrumentFetch: function() { },

    /**
     * Request boomerang to send its beacon with all queued beacon data
     * (via {@link BOOMR.addVar}).
     *
     * Boomerang may ignore this request.
     *
     * When this method is called, boomerang checks all plugins. If any
     * plugin has not completed its checks (ie, the plugin's `is_complete()`
     * method returns `false`, then this method does nothing.
     *
     * If all plugins have completed, then this method fires the
     * {@link BOOMR#event:before_beacon} event with all variables that will be
     * sent on the beacon.
     *
     * After all {@link BOOMR#event:before_beacon} handlers return, this method
     * checks if a `beacon_url` has been configured and if there are any
     * beacon parameters to be sent. If both are true, it fires the beacon.
     *
     * The {@link BOOMR#event:beacon} event is then fired.
     *
     * `sendBeacon()` should be called any time a plugin goes from
     * `is_complete() = false` to `is_complete = true` so the beacon is
     * sent.
     *
     * The actual beaconing is handled in {@link BOOMR.real_sendBeacon} after
     * a short delay (via {@link BOOMR.setImmediate}).  If other calls to
     * `sendBeacon` happen before {@link BOOMR.real_sendBeacon} is called,
     * those calls will be discarded (so it's OK to call this in quick
     * succession).
     *
     * @param {string} [beacon_url_override] Beacon URL override
     *
     * @memberof BOOMR
     */
    sendBeacon: function(beacon_url_override) {
      // This plugin wants the beacon to go somewhere else,
      // so update the location
      if (beacon_url_override) {
        impl.beacon_url_override = beacon_url_override;
      }

      if (!impl.beaconQueued) {
        impl.beaconQueued = true;
        BOOMR.setImmediate(BOOMR.real_sendBeacon, null, null, BOOMR);
      }

      return true;
    },

    /**
     * Sends a beacon when the beacon queue is empty.
     *
     * @param {object} params Beacon parameters to set
     * @param {function} callback Callback to run when the queue is ready
     * @param {object} that Function to apply callback to
     */
    sendBeaconWhenReady: function(params, callback, that) {
      // If we're already sending a beacon, wait until the queue is empty
      if (impl.beaconInQueue) {
        // wait until the beacon is sent, then try again
        BOOMR.subscribe("beacon", function() {
          BOOMR.sendBeaconWhenReady(params, callback, that);
        }, null, BOOMR, true);

        return;
      }

      // Lock the beacon queue
      impl.beaconInQueue = true;

      // add all parameters
      for (var paramName in params) {
        if (params.hasOwnProperty(paramName)) {
          // add this data to a single beacon
          BOOMR.addVar(paramName, params[paramName], true);
        }
      }

      // run the callback
      if (typeof callback === "function" && typeof that !== "undefined") {
        callback.apply(that);
      }

      // send the beacon
      BOOMR.sendBeacon();
    },

    /**
     * Sends all beacon data.
     *
     * This function should be called directly any time a "new" beacon is about
     * to be constructed.  For example, if you're creating a new XHR or other
     * custom beacon, you should ensure the existing beacon data is flushed
     * by calling `BOOMR.real_sendBeacon();` first.
     *
     * @memberof BOOMR
     */
    real_sendBeacon: function() {
      var k, form, url,
          errors = [],
          params = [],
          paramsJoined,
          varsSent = {};

      if (!impl.beaconQueued) {
        return false;
      }

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("send_beacon:start");
      /* END_DEBUG */

      impl.beaconQueued = false;

      BOOMR.debug("Checking if we can send beacon");

      // At this point someone is ready to send the beacon.  We send
      // the beacon only if all plugins have finished doing what they
      // wanted to do
      for (k in this.plugins) {
        if (this.plugins.hasOwnProperty(k)) {
          if (impl.disabled_plugins[k]) {
            continue;
          }

          if (!this.plugins[k].is_complete(impl.vars)) {
            BOOMR.debug("Plugin " + k + " is not complete, deferring beacon send");
            // if an Early beacon is blocked, then we'll cancel it.
            // By removing the `early` param, the beacon params will be merged
            // with the following load beacon.
            delete impl.vars.early;

            return false;
          }
        }
      }

      // Sanity test that the browser is still available (and not shutting down)
      if (!window || !window.Image || !window.navigator || !BOOMR.window) {
        BOOMR.debug("DOM not fully available, not sending a beacon");

        return false;
      }

      // For SPA apps, don't strip hashtags as some SPA frameworks use #s for tracking routes
      // instead of History pushState() APIs. Use d.URL instead of location.href because of a
      // Safari bug.
      var isSPA = BOOMR.utils.inArray(impl.vars["http.initiator"], BOOMR.constants.BEACON_TYPE_SPAS);
      var isPageLoad = typeof impl.vars["http.initiator"] === "undefined" || isSPA;

      if (!impl.vars.pgu) {
        impl.vars.pgu = isSPA ? d.URL : d.URL.replace(/#.*/, "");
      }

      impl.vars.pgu = BOOMR.utils.cleanupURL(impl.vars.pgu);

      // Use the current document.URL if it hasn't already been set, or for SPA apps,
      // on each new beacon (since each SPA soft navigation might change the URL)
      if (!impl.vars.u || isSPA) {
        impl.vars.u = impl.vars.pgu;
      }

      if (impl.vars.pgu === impl.vars.u) {
        delete impl.vars.pgu;
      }

      // Add cleaned-up referrer URLs to the beacon, if available
      if (impl.r) {
        impl.vars.r = BOOMR.utils.cleanupURL(impl.r);
      }
      else {
        delete impl.vars.r;
      }

      impl.vars.v = BOOMR.version;

      // Snippet version, if available
      if (BOOMR.snippetVersion) {
        impl.vars.sv = BOOMR.snippetVersion;
      }

      // Snippet method is IFRAME if not specified (pre-v12 snippets)
      impl.vars.sm = BOOMR.snippetMethod || "i";

      if (BOOMR.session.enabled) {
        impl.vars["rt.si"] = BOOMR.session.ID + "-" + Math.round(BOOMR.session.start / 1000).toString(36);
        impl.vars["rt.ss"] = BOOMR.session.start;

        if (typeof impl.vars.early === "undefined") {
          // make sure Session Length is always at least 1 for non-Early beacons
          impl.vars["rt.sl"] = BOOMR.session.length >= 1 ? BOOMR.session.length : 1;
        }
        else {
          impl.vars["rt.sl"] = BOOMR.session.length;
        }
      }
      else {
        BOOMR.removeVar("rt.si", "rt.ss", "rt.sl");
      }

      if (BOOMR.visibilityState()) {
        impl.vars["vis.st"] = BOOMR.visibilityState();

        if (BOOMR.lastVisibilityEvent.visible) {
          impl.vars["vis.lv"] = BOOMR.now() - BOOMR.lastVisibilityEvent.visible;
        }

        if (BOOMR.lastVisibilityEvent.hidden) {
          impl.vars["vis.lh"] = BOOMR.now() - BOOMR.lastVisibilityEvent.hidden;
        }
      }

      var platform = "";

      if (navigator.userAgentData && typeof navigator.userAgentData.platform === "string") {
        platform = navigator.userAgentData.platform;
      }
      else {
        platform = navigator.platform;
      }

      impl.vars["ua.plt"] = platform;
      impl.vars["ua.vnd"] = navigator.vendor;

      // if userAgentData exists, then store on the beacon
      if (impl.userAgentData) {
        impl.vars["ua.arch"] = impl.userAgentData.architecture;
        impl.vars["ua.model"] = impl.userAgentData.model;
        impl.vars["ua.pltv"] = impl.userAgentData.platformVersion;
      }

      if (this.pageId) {
        impl.vars.pid = this.pageId;
      }

      // add beacon number
      impl.vars.n = ++this.beaconsSent;

      if (w !== window) {
        impl.vars["if"] = "";
      }

      for (k in impl.errors) {
        if (impl.errors.hasOwnProperty(k)) {
          errors.push(k + (impl.errors[k] > 1 ? " (*" + impl.errors[k] + ")" : ""));
        }
      }

      if (errors.length > 0) {
        impl.vars.errors = errors.join("\n");
      }

      impl.errors = {};

      // If we reach here, all plugins have completed
      impl.fireEvent("before_beacon", impl.vars);

      // clone the vars object for two reasons: first, so all listeners of
      // 'beacon' get an exact clone (in case listeners are doing
      // BOOMR.removeVar), and second, to help build our priority list of vars.
      for (k in impl.vars) {
        if (impl.vars.hasOwnProperty(k)) {
          varsSent[k] = impl.vars[k];
        }
      }

      BOOMR.removeVar(["qt", "pgu"]);

      if (typeof impl.vars.early === "undefined") {
        // remove any vars that should only be on a single beacon.
        // Early beacons don't clear vars even if flagged as `singleBeacon` so
        // that they can be re-sent on the next normal beacon
        for (var singleVarName in impl.singleBeaconVars) {
          if (impl.singleBeaconVars.hasOwnProperty(singleVarName)) {
            BOOMR.removeVar(singleVarName);
          }
        }

        // clear single beacon vars list
        impl.singleBeaconVars = {};

        // keep track of page load beacons
        if (!impl.hasSentPageLoadBeacon && isPageLoad) {
          impl.hasSentPageLoadBeacon = true;

          // let this beacon go out first
          BOOMR.setImmediate(function() {
            impl.fireEvent("page_load_beacon", varsSent);
          });
        }
      }

      // Stop at this point if we are rate limited
      if (BOOMR.session.rate_limited) {
        BOOMR.debug("Skipping because we're rate limited");

        return false;
      }

      // mark that we're no longer sending a beacon now, as those
      // paying attention to this will trigger at the beacon event
      impl.beaconInQueue = false;

      // send the beacon data
      BOOMR.sendBeaconData(varsSent);

      /* BEGIN_DEBUG */
      BOOMR.utils.mark("send_beacon:end");
      BOOMR.utils.measure(
        "send_beacon",
        "send_beacon:start",
        "send_beacon:end");
      /* END_DEBUG */

      return true;
    },

    /**
     * Sends beacon data via the Beacon API, XHR or Image
     *
     * @param {object} data Data
     */
    sendBeaconData: function(data) {
      var urlFirst = [],
          urlLast = [],
          params, paramsJoined,
          url, img,
          useImg = true,
          xhr, ret;

      BOOMR.debug("Ready to send beacon: " + BOOMR.utils.objectToString(data));

      // Use the override URL if given
      impl.beacon_url = impl.beacon_url_override || impl.beacon_url;

      // Check that the beacon_url was set first
      if (!impl.beacon_url) {
        BOOMR.debug("No beacon URL, so skipping.");

        return false;
      }

      if (!impl.beaconUrlAllowed(impl.beacon_url)) {
        BOOMR.debug("Beacon URL not allowed: " + impl.beacon_url);

        return false;
      }

      // Check that we have data to send
      if (BOOMR.utils.isObjectEmpty(data)) {
        return false;
      }

      // If we reach here, we've figured out all of the beacon data we'll send.
      impl.fireEvent("beacon", data);

      // get high- and low-priority variables first, which remove any of
      // those vars from data
      urlFirst = this.getVarsOfPriority(data, -1);
      urlLast  = this.getVarsOfPriority(data, 1);

      // merge the 3 lists
      params = urlFirst.concat(this.getVarsOfPriority(data, 0), urlLast);
      paramsJoined = params.join("&");

      // If beacon_url is protocol relative, make it https only
      if (impl.beacon_url_force_https && impl.beacon_url.match(/^\/\//)) {
        impl.beacon_url = "https:" + impl.beacon_url;
      }

      // if there are already url parameters in the beacon url,
      // change the first parameter prefix for the boomerang url parameters to &
      url = impl.beacon_url + ((impl.beacon_url.indexOf("?") > -1) ? "&" : "?") + paramsJoined;

      //
      // Try to send an IMG beacon if possible (which is the most compatible),
      // otherwise send an XHR beacon if the  URL length is longer than 2,000 bytes.
      //
      if (impl.beacon_type === "GET") {
        useImg = true;

        if (url.length > BOOMR.constants.MAX_GET_LENGTH) {
          ((window.console && (console.warn || console.log)) || function() {})(
            "Boomerang: Warning: Beacon may not be sent via GET due to payload size > 2000 bytes"
          );
        }
      }
      else if (impl.beacon_type === "POST" || url.length > BOOMR.constants.MAX_GET_LENGTH) {
        // switch to a XHR beacon if the the user has specified a POST OR GET length is too long
        useImg = false;
      }

      //
      // Try the sendBeacon API first.
      // But if beacon_type is set to "GET", dont attempt
      // sendBeacon API call
      //
      if (w && w.navigator &&
          typeof w.navigator.sendBeacon === "function" &&
          BOOMR.utils.isNative(w.navigator.sendBeacon) &&
          typeof w.Blob === "function" &&
          impl.beacon_type !== "GET" &&
          // As per W3C, The sendBeacon method does not provide ability to pass any
          // header other than 'Content-Type'. So if we need to send data with
          // 'Authorization' header, we need to fallback to good old xhr.
          typeof impl.beacon_auth_token === "undefined" &&
          !impl.beacon_disable_sendbeacon) {
        // note we're using sendBeacon with &sb=1
        var blobData = new w.Blob([paramsJoined + "&sb=1"], {
          type: "application/x-www-form-urlencoded"
        });

        if (w.navigator.sendBeacon(impl.beacon_url, blobData)) {
          return true;
        }

        // sendBeacon was not successful, try Image or XHR beacons
      }

      // If we don't have XHR available, force an image beacon and hope
      // for the best
      if (!BOOMR.orig_XMLHttpRequest && (!w || !w.XMLHttpRequest)) {
        useImg = true;
      }

      if (useImg) {
        //
        // Image beacon
        //

        // just in case Image isn't a valid constructor
        try {
          img = new Image();
        }
        catch (e) {
          BOOMR.debug("Image is not a constructor, not sending a beacon");

          return false;
        }

        img.src = url;
      }
      else {
        //
        // XHR beacon
        //

        // Send a form-encoded XHR POST beacon
        xhr = new (BOOMR.window.orig_XMLHttpRequest || BOOMR.orig_XMLHttpRequest || BOOMR.window.XMLHttpRequest)();
        try {
          this.sendXhrPostBeacon(xhr, paramsJoined);
        }
        catch (e) {
          // if we had an exception with the window XHR object, try our IFRAME XHR
          xhr = new BOOMR.boomerang_frame.XMLHttpRequest();
          this.sendXhrPostBeacon(xhr, paramsJoined);
        }
      }

      return true;
    },

    /**
     * Determines whether or not a Page Load beacon has been sent.
     *
     * @returns {boolean} True if a Page Load beacon has been sent.
     *
     * @memberof BOOMR
     */
    hasSentPageLoadBeacon: function() {
      return impl.hasSentPageLoadBeacon;
    },

    /**
     * Sends a beacon via XMLHttpRequest
     *
     * @param {object} xhr XMLHttpRequest object
     * @param {object} [paramsJoined] XMLHttpRequest.send() argument
     *
     * @memberof BOOMR
     */
    sendXhrPostBeacon: function(xhr, paramsJoined) {
      xhr.open("POST", impl.beacon_url);

      xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

      if (typeof impl.beacon_auth_token !== "undefined") {
        if (typeof impl.beacon_auth_key === "undefined") {
          impl.beacon_auth_key = "Authorization";
        }

        xhr.setRequestHeader(impl.beacon_auth_key, impl.beacon_auth_token);
      }

      if (impl.beacon_with_credentials) {
        xhr.withCredentials = true;
      }

      xhr.send(paramsJoined);
    },

    /**
     * Gets all variables of the specified priority
     *
     * @param {object} vars Variables (will be modified for pri -1 and 1)
     * @param {number} pri Priority (-1, 0, or 1)
     *
     * @return {string[]} Array of URI-encoded vars
     *
     * @memberof BOOMR
     */
    getVarsOfPriority: function(vars, pri) {
      var name,
          url = [],
          // if we were given a priority, iterate over that list
          // else iterate over vars
          iterVars = (pri !== 0 ? impl.varPriority[pri] : vars);

      for (name in iterVars) {
        // if this var is set, add it to our URL array
        if (iterVars.hasOwnProperty(name) && vars.hasOwnProperty(name)) {
          url.push(this.getUriEncodedVar(name, typeof vars[name] === "undefined" ? "" : vars[name]));

          // remove this name from vars so it isn't also added
          // to the non-prioritized list when pri=0 is called
          if (pri !== 0) {
            delete vars[name];
          }
        }
      }

      return url;
    },

    /**
     * Gets a URI-encoded name/value pair.
     *
     * @param {string} name Name
     * @param {string} value Value
     *
     * @returns {string} URI-encoded string
     *
     * @memberof BOOMR
     */
    getUriEncodedVar: function(name, value) {
      if (value === undefined || value === null) {
        value = "";
      }

      if (typeof value === "object") {
        value = BOOMR.utils.serializeForUrl(value);
      }

      var result = encodeURIComponent(name) +
        "=" + encodeURIComponent(value);

      return result;
    },

    /**
     * Gets the latest ResourceTiming entry for the specified URL.
     *
     * Default sort order is chronological startTime.
     *
     * @param {string} url Resource URL
     * @param {function} [sort] Sort the entries before returning the last one
     * @param {function} [filter] Filter the entries. Will be applied before sorting
     *
     * @returns {PerformanceEntry|undefined} Entry, or undefined if ResourceTiming is not
     *  supported or if the entry doesn't exist
     *
     * @memberof BOOMR
     */
    getResourceTiming: function(url, sort, filter) {
      var entries,
          p = BOOMR.getPerformance();

      try {
        if (p && typeof p.getEntriesByName === "function") {
          entries = p.getEntriesByName(url);

          if (!entries || !entries.length) {
            return;
          }

          if (typeof filter === "function") {
            entries = BOOMR.utils.arrayFilter(entries, filter);

            if (!entries || !entries.length) {
              return;
            }
          }

          if (entries.length > 1 && typeof sort === "function") {
            entries.sort(sort);
          }

          return entries[entries.length - 1];
        }
      }
      catch (e) {
        BOOMR.warn("getResourceTiming:" + e);
      }
    },

    /**
     * Determines whether beacon data is for a Page Load beacon, or not.
     *
     * Page Load beacons include regular Page Loads, SPA Hard or SPA Soft beacons.
     *
     * We also consider an Aborted Load beacon a Page Load.
     *
     * @param {object} data Beacon Data
     * @returns {boolean} True if beacon data is for a Page Load beacon
     */
    isPageLoadBeacon: function(data) {
      return (typeof data["rt.quit"] === "undefined" || typeof data["rt.abld"] !== "undefined") &&
        (typeof data["http.initiator"] === "undefined" ||
          BOOMR.utils.inArray(data["http.initiator"], BOOMR.constants.BEACON_TYPE_SPAS));
    }

    /* BEGIN_DEBUG */,
    /**
     * Sets the list of allowed Beacon URLs
     *
     * @param {string[]} urls List of string regular expressions
     */
    setBeaconUrlsAllowed: function(urls) {
      impl.beacon_urls_allowed = urls;
    }
    /* END_DEBUG */
  };

  // if not already set already on BOOMR, determine the URL
  if (!BOOMR.url) {
    boomr.url = boomr.utils.getMyURL();
  }
  else {
    // canonicalize the URL
    var a = BOOMR.window.document.createElement("a");

    a.href = BOOMR.url;
    boomr.url = a.href;
  }

  delete BOOMR_start;

  /**
   * @global
   * @type {TimeStamp}
   * @name BOOMR_lstart
   * @desc
   * This variable is added to the global scope (`window`) until Boomerang loads,
   * at which point it is removed.
   *
   * Time the loader script started fetching boomerang.js (if the asynchronous
   * loader snippet is used).
   */
  if (typeof BOOMR_lstart === "number") {
    /**
     * Time the loader script started fetching boomerang.js (if using the
     * asynchronous loader snippet) (`BOOMR_lstart`)
     * @type {TimeStamp}
     *
     * @memberof BOOMR
     */
    boomr.t_lstart = BOOMR_lstart;
    delete BOOMR_lstart;
  }
  else if (typeof BOOMR.window.BOOMR_lstart === "number") {
    boomr.t_lstart = BOOMR.window.BOOMR_lstart;
  }

  /**
   * This variable is added to the global scope (`window`).
   *
   * Time the `window.onload` event fired (if using the asynchronous loader snippet).
   *
   * This timestamp is logged in the case boomerang.js loads after the onload event
   * for browsers that don't support NavigationTiming.
   *
   * @global
   * @name BOOMR_onload
   * @type {TimeStamp}
   */
  if (typeof BOOMR.window.BOOMR_onload === "number") {
    /**
     * Time the `window.onload` event fired (if using the asynchronous loader snippet).
     *
     * This timestamp is logged in the case boomerang.js loads after the onload event
     * for browsers that don't support NavigationTiming.
     *
     * @type {TimeStamp}
     * @memberof BOOMR
     */
    boomr.t_onload = BOOMR.window.BOOMR_onload;
  }

  (function() {
    var make_logger;

    if (typeof console === "object" && console.log !== undefined) {
      /**
       * Logs the message to the console
       *
       * @param {string} m Message
       * @param {string} l Log level
       * @param {string} [s] Source
       *
       * @function log
       *
       * @memberof BOOMR
       */
      boomr.log = function(m, l, s) {
        console.log("(" + BOOMR.now() + ") " +
          "{" + BOOMR.pageId + "}" +
          ": " + s +
          ": [" + l + "] " +
          m);
      };
    }
    else {
      // NOP for browsers that don't support it
      boomr.log = function() {};
    }

    make_logger = function(l) {
      return function(m, s) {
        this.log(m, l, "boomerang" + (s ? "." + s : ""));

        return this;
      };
    };

    /**
     * Logs debug messages to the console
     *
     * Debug messages are stripped out of production builds.
     *
     * @param {string} m Message
     * @param {string} [s] Source
     *
     * @function debug
     *
     * @memberof BOOMR
     */
    boomr.debug = make_logger("debug");

    /**
     * Logs info messages to the console
     *
     * @param {string} m Message
     * @param {string} [s] Source
     *
     * @function info
     *
     * @memberof BOOMR
     */
    boomr.info = make_logger("info");

    /**
     * Logs warning messages to the console
     *
     * @param {string} m Message
     * @param {string} [s] Source
     *
     * @function warn
     *
     * @memberof BOOMR
     */
    boomr.warn = make_logger("warn");

    /**
     * Logs error messages to the console
     *
     * @param {string} m Message
     * @param {string} [s] Source
     *
     * @function error
     *
     * @memberof BOOMR
     */
    boomr.error = make_logger("error");
  }());

  // If the browser supports performance.now(), swap that in for BOOMR.now
  try {
    var p = boomr.getPerformance();

    if (p &&
        typeof p.now === "function" &&
        // #545 handle bogus performance.now from broken shims
        /\[native code\]/.test(String(p.now)) &&
        p.timing &&
        p.timing.navigationStart) {
      boomr.now = function() {
        return Math.round(p.now() + p.timing.navigationStart);
      };
    }
  }
  catch (ignore) {
    // empty
  }

  impl.checkLocalStorageSupport();

  (function() {
    var ident;

    for (ident in boomr) {
      if (boomr.hasOwnProperty(ident)) {
        BOOMR[ident] = boomr[ident];
      }
    }

    if (!BOOMR.xhr_excludes) {
      /**
       * URLs to exclude from automatic `XMLHttpRequest` instrumentation.
       *
       * You can put any of the following in it:
       * * A full URL
       * * A hostname
       * * A path
       *
       * @example
       * BOOMR = window.BOOMR || {};
       * BOOMR.xhr_excludes = {
       *   "mysite.com": true,
       *   "/dashboard/": true,
       *   "https://mysite.com/dashboard/": true
       * };
       *
       * @memberof BOOMR
       */
      BOOMR.xhr_excludes = {};
    }
  }());

  /* BEGIN_DEBUG */
  /*
   * This block reports on overridden functions on `window` and properties on `document` using `BOOMR.warn()`.
   * To enable, add `overridden` with a value of `true` to the query string.
   */
  (function() {
    /**
     * Checks a window for overridden functions.
     *
     * @param {Window} win The window object under test
     *
     * @returns {Array} Array of overridden function names
     */
    BOOMR.checkWindowOverrides = function(win) {
      if (!Object.getOwnPropertyNames) {
        return [];
      }

      var freshWindow, objects,
          overridden = [];

      function setup() {
        var iframe = d.createElement("iframe");

        iframe.style.display = "none";
        iframe.src = "javascript:false"; // eslint-disable-line no-script-url
        d.getElementsByTagName("script")[0].parentNode.appendChild(iframe);
        freshWindow = iframe.contentWindow;
        objects = Object.getOwnPropertyNames(freshWindow);
      }

      function teardown() {
        iframe.parentNode.removeChild(iframe);
      }

      function checkWindowObject(objectKey) {
        if (isNonNative(objectKey)) {
          overridden.push(objectKey);
        }
      }

      function isNonNative(key) {
        var split = key.split("."),
            fn = win,
            results = [];

        while (fn && split.length) {
          try {
            fn = fn[split.shift()];
          }
          catch (e) {
            return false;
          }
        }

        return typeof fn === "function" && !isNativeFunction(fn, key);
      }

      function isNativeFunction(fn, str) {
        if (str === "console.assert" ||
          str === "Function.prototype" ||
          str.indexOf("onload") >= 0 ||
          str.indexOf("onbeforeunload") >= 0 ||
          str.indexOf("onerror") >= 0 ||
          str.indexOf("onload") >= 0 ||
          str.indexOf("NodeFilter") >= 0) {
          return true;
        }

        return fn.toString &&
          !fn.hasOwnProperty("toString") &&
          /\[native code\]/.test(String(fn));
      }

      setup();
      for (var objectIndex = 0; objectIndex < objects.length; objectIndex++) {
        var objectKey = objects[objectIndex];

        if (objectKey === "window" ||
          objectKey === "self" ||
          objectKey === "top" ||
          objectKey === "parent" ||
          objectKey === "frames") {
          continue;
        }

        if (freshWindow[objectKey] &&
          (typeof freshWindow[objectKey] === "object" || typeof freshWindow[objectKey] === "function")) {
          checkWindowObject(objectKey);

          var propertyNames = [];

          try {
            propertyNames = Object.getOwnPropertyNames(freshWindow[objectKey]);
          }
          catch (e) {
            ;
          }

          for (var i = 0; i < propertyNames.length; i++) {
            checkWindowObject([objectKey, propertyNames[i]].join("."));
          }

          if (freshWindow[objectKey].prototype) {
            propertyNames = Object.getOwnPropertyNames(freshWindow[objectKey].prototype);
            for (var i = 0; i < propertyNames.length; i++) {
              checkWindowObject([objectKey, "prototype", propertyNames[i]].join("."));
            }
          }
        }
      }

      return overridden;
    };

    /**
     * Checks a document for overridden properties.
     *
     * @param {HTMLDocument} doc The document object under test
     *
     * @returns {Array} Array of overridden properties names
     */
    BOOMR.checkDocumentOverrides = function(doc) {
      return BOOMR.utils.arrayFilter(["readyState", "domain", "hidden", "URL", "cookie"], function(key) {
        return doc.hasOwnProperty(key);
      });
    };

    if (BOOMR.utils.getQueryParamValue("overridden") === "true" && w && w.Object && Object.getOwnPropertyNames) {
      var overridden = []
        .concat(BOOMR.checkWindowOverrides(w))
        .concat(BOOMR.checkDocumentOverrides(d));

      if (overridden.length > 0) {
        BOOMR.warn("overridden: " + overridden.sort());
      }
    }
  })();
  /* END_DEBUG */

  dispatchEvent("onBoomerangLoaded", { "BOOMR": BOOMR }, true);
}(window));

// end of boomerang beaconing section