backbone.layoutmanager.js

/*!
 * backbone.layoutmanager.js v0.9.3
 * Copyright 2013, Tim Branyen (@tbranyen)
 * backbone.layoutmanager.js may be freely distributed under the MIT license.
 */
(function(window, factory) {
  "use strict";
  var Backbone = window.Backbone;

  // AMD. Register as an anonymous module.  Wrap in function so we have access
  // to root via `this`.
  if (typeof define === "function" && define.amd) {
    return define(["backbone", "underscore", "jquery"], function() {
      return factory.apply(window, arguments);
    });
  }

  // Browser globals.
  Backbone.Layout = factory.call(window, Backbone, window._, Backbone.$);
}(typeof global === "object" ? global : this, function (Backbone, _, $) {
"use strict";

// Create a reference to the global object. In browsers, it will map to the
// `window` object; in Node, it will be `global`.
var window = this;

// Hoisted, referenced at the bottom of the source.  This caches a list of all
// LayoutManager options at definition time.
var keys;

// Maintain references to the two `Backbone.View` functions that are
// overwritten so that they can be proxied.
var _configure = Backbone.View.prototype._configure;

// Cache these methods for performance.
var aPush = Array.prototype.push;
var aConcat = Array.prototype.concat;
var aSplice = Array.prototype.splice;
var trim = String.prototype.trim ?
  _.bind(String.prototype.trim.call, String.prototype.trim) :
  $.trim;

// LayoutManager is a wrapper around a `Backbone.View`.
var LayoutManager = Backbone.View.extend({
  _render: function(options) {
    // Keep the view consistent between callbacks and deferreds.
    var view = this;
    // Shorthand the manager.
    var manager = view.__manager__;
    // Cache these properties.
    var beforeRender = options.beforeRender;
    // Create a deferred instead of going off
    var def = options.deferred();

    // Ensure all nested Views are properly scrubbed if re-rendering.
    if (view.hasRendered) {
      view._removeViews();
    }

    // This continues the render flow after `beforeRender` has completed.
    manager.callback = function() {
      // Clean up asynchronous manager properties.
      delete manager.isAsync;
      delete manager.callback;

      // Always emit a beforeRender event.
      view.trigger("beforeRender", view);

      // Render!
      view._viewRender(options, manager).render().then(function() {
        // Complete this deferred once resolved.
        def.resolve();
      });
    };

    // If a beforeRender function is defined, call it.
    if (beforeRender) {
      beforeRender.call(view, view);
    }

    if (!manager.isAsync) {
      manager.callback();
    }

    // Return this intermediary promise.
    return def.promise();
  },

  // This function is responsible for pairing the rendered template into the
  // DOM element.
  _applyTemplate: function(rendered, options, manager, def) {
    // Actually put the rendered contents into the element.
    if (_.isString(rendered)) {
      // If no container is specified, we must replace the content.
      if (manager.noel) {
        rendered = $.parseHTML(rendered, true);

        // Remove extra root elements.
        this.$el.slice(1).remove();

        // Swap out the View on the first top level element to avoid
        // duplication.
        this.$el.replaceWith(rendered);

        // Don't delegate events here - we'll do that in resolve()
        this.setElement(rendered, false);
      } else {
        options.html(this.$el, rendered);
      }
    }

    // Resolve only after fetch and render have succeeded.
    def.resolveWith(this, [this]);
  },

  // Creates a deferred and returns a function to call when finished.
  // This gets passed to all _render methods.  The `root` value here is passed
  // from the `manage(this).render()` line in the `_render` function
  _viewRender: function(options, manager) {
    var url, contents, def;
    var root = this;

    // Once the template is successfully fetched, use its contents to proceed.
    // Context argument is first, since it is bound for partial application
    // reasons.
    function done(context, template) {
      // Store the rendered template someplace so it can be re-assignable.
      var rendered;

      // Trigger this once the render method has completed.
      manager.callback = function(rendered) {
        // Clean up asynchronous manager properties.
        delete manager.isAsync;
        delete manager.callback;

        root._applyTemplate(rendered, options, manager, def);
      };

      // Ensure the cache is up-to-date.
      LayoutManager.cache(url, template);

      // Render the View into the el property.
      if (template) {
        rendered = options.renderTemplate.call(root, template, context);
      }

      // If the function was synchronous, continue execution.
      if (!manager.isAsync) {
        root._applyTemplate(rendered, options, manager, def);
      }
    }

    return {
      // This `render` function is what gets called inside of the View render,
      // when `manage(this).render` is called.  Returns a promise that can be
      // used to know when the element has been rendered into its parent.
      render: function() {
        var context = root.serialize || options.serialize;
        var template = root.template || options.template;

        // Create a deferred specifically for fetching.
        def = options.deferred();

        // If data is a function, immediately call it.
        if (_.isFunction(context)) {
          context = context.call(root);
        }

        // Set the internal callback to trigger once the asynchronous or
        // synchronous behavior has completed.
        manager.callback = function(contents) {
          // Clean up asynchronous manager properties.
          delete manager.isAsync;
          delete manager.callback;

          done(context, contents);
        };

        // Set the url to the prefix + the view's template property.
        if (typeof template === "string") {
          url = options.prefix + template;
        }

        // Check if contents are already cached and if they are, simply process
        // the template with the correct data.
        if (contents = LayoutManager.cache(url)) {
          done(context, contents, url);

          return def;
        }

        // Fetch layout and template contents.
        if (typeof template === "string") {
          contents = options.fetchTemplate.call(root, options.prefix +
            template);
        // If the template is already a function, simply call it.
        } else if (typeof template === "function") {
          contents = template;
        // If its not a string and not undefined, pass the value to `fetch`.
        } else if (template != null) {
          contents = options.fetchTemplate.call(root, template);
        }

        // If the function was synchronous, continue execution.
        if (!manager.isAsync) {
          done(context, contents);
        }

        return def;
      }
    };
  },

  // This named function allows for significantly easier debugging.
  constructor: function Layout(options) {
    // Grant this View superpowers.
    this.manage = true;

    // Have Backbone set up the rest of this View.
    Backbone.View.call(this, options);
  },

  // This method is used within specific methods to indicate that they should
  // be treated as asynchronous.  This method should only be used within the
  // render chain, otherwise unexpected behavior may occur.
  async: function() {
    var manager = this.__manager__;

    // Set this View's action to be asynchronous.
    manager.isAsync = true;

    // Return the callback.
    return manager.callback;
  },

  promise: function() {
    return this.__manager__.renderDeferred.promise();
  },

  // Sometimes it's desirable to only render the child views under the parent.
  // This is typical for a layout that does not change.  This method will
  // iterate over the child Views and aggregate all child render promises and
  // return the parent View.  The internal `promise()` method will return the
  // aggregate promise that resolves once all children have completed their
  // render.
  renderViews: function() {
    var root = this;
    var manager = root.__manager__;
    var options = root.getAllOptions();
    var newDeferred = options.deferred();

    // Collect all promises from rendering the child views and wait till they
    // all complete.
    var promises = root.getViews().map(function(view) {
      return view.render().__manager__.renderDeferred;
    }).value();

    // Simulate a parent render to remain consistent.
    manager.renderDeferred = newDeferred.promise();

    // Once all child views have completed rendering, resolve parent deferred
    // with the correct context.
    options.when(promises).then(function() {
      newDeferred.resolveWith(root, [root]);
    });

    // Allow this method to be chained.
    return root;
  },

  // Shorthand to `setView` function with the `insert` flag set.
  insertView: function(selector, view) {
    // If the `view` argument exists, then a selector was passed in.  This code
    // path will forward the selector on to `setView`.
    if (view) {
      return this.setView(selector, view, true);
    }

    // If no `view` argument is defined, then assume the first argument is the
    // View, somewhat now confusingly named `selector`.
    return this.setView(selector, true);
  },

  // Iterate over an object and ensure every value is wrapped in an array to
  // ensure they will be inserted, then pass that object to `setViews`.
  insertViews: function(views) {
    // If an array of views was passed it should be inserted into the
    // root view. Much like calling insertView without a selector.
    if (_.isArray(views)) {
      return this.setViews({ "": views });
    }

    _.each(views, function(view, selector) {
      views[selector] = _.isArray(view) ? view : [view];
    });

    return this.setViews(views);
  },

  // Returns the View that matches the `getViews` filter function.
  getView: function(fn) {
    // If `getView` is invoked with undefined as the first argument, then the
    // second argument will be used instead.  This is to allow
    // `getViews(undefined, fn)` to work as `getViews(fn)`.  Useful for when
    // you are allowing an optional selector.
    if (fn == null) {
      fn = arguments[1];
    }

    return this.getViews(fn).first().value();
  },

  // Provide a filter function to get a flattened array of all the subviews.
  // If the filter function is omitted it will return all subviews.  If a
  // String is passed instead, it will return the Views for that selector.
  getViews: function(fn) {
    var views;

    // If the filter argument is a String, then return a chained Version of the
    // elements. The value at the specified filter may be undefined, a single
    // view, or an array of views; in all cases, chain on a flat array.
    if (typeof fn === "string") {
      fn = this.sections[fn] || fn;
      views = this.views[fn] || [];

      // If Views is undefined you are concatenating an `undefined` to an array
      // resulting in a value being returned.  Defaulting to an array prevents
      // this.
      //return _.chain([].concat(views || []));
      return _.chain([].concat(views));
    }

    // Generate an array of all top level (no deeply nested) Views flattened.
    views = _.chain(this.views).map(function(view) {
      return _.isArray(view) ? view : [view];
    }, this).flatten();

    // If the argument passed is an Object, then pass it to `_.where`.
    if (typeof fn === "object") {
      return views.where(fn);
    }

    // If a filter function is provided, run it on all Views and return a
    // wrapped chain. Otherwise, simply return a wrapped chain of all Views.
    return typeof fn === "function" ? views.filter(fn) : views;
  },

  // Use this to remove Views, internally uses `getViews` so you can pass the
  // same argument here as you would to that method.
  removeView: function(fn) {
    // Allow an optional selector or function to find the right model and
    // remove nested Views based off the results of the selector or filter.
    return this.getViews(fn).each(function(nestedView) {
      nestedView.remove();
    });
  },

  // This takes in a partial name and view instance and assigns them to
  // the internal collection of views.  If a view is not a LayoutManager
  // instance, then mix in the LayoutManager prototype.  This ensures
  // all Views can be used successfully.
  //
  // Must definitely wrap any render method passed in or defaults to a
  // typical render function `return layout(this).render()`.
  setView: function(name, view, insert) {
    var manager, options, selector;
    // Parent view, the one you are setting a View on.
    var root = this;

    // If no name was passed, use an empty string and shift all arguments.
    if (typeof name !== "string") {
      insert = view;
      view = name;
      name = "";
    }

    // Shorthand the `__manager__` property.
    manager = view.__manager__;

    // If the View has not been properly set up, throw an Error message
    // indicating that the View needs `manage: true` set.
    if (!manager) {
      throw new Error("The argument associated with selector '" + name +
        "' is defined and a View.  Set `manage` property to true for " +
        "Backbone.View instances.");
    }

    // Assign options.
    options = view.getAllOptions();

    // Add reference to the parentView.
    manager.parent = root;

    // Add reference to the placement selector used.
    selector = manager.selector = root.sections[name] || name;

    // Code path is less complex for Views that are not being inserted.  Simply
    // remove existing Views and bail out with the assignment.
    if (!insert) {
      // If the View we are adding has already been rendered, simply inject it
      // into the parent.
      if (view.hasRendered) {
        // Apply the partial.
        options.partial(root.$el, view.$el, root.__manager__, manager);
      }

      // Ensure remove is called when swapping View's.
      root.removeView(name);

      // Assign to main views object and return for chainability.
      return root.views[selector] = view;
    }

    // Ensure this.views[selector] is an array and push this View to
    // the end.
    root.views[selector] = aConcat.call([], root.views[name] || [], view);

    // Put the parent view into `insert` mode.
    root.__manager__.insert = true;

    return view;
  },

  // Allows the setting of multiple views instead of a single view.
  setViews: function(views) {
    // Iterate over all the views and use the View's view method to assign.
    _.each(views, function(view, name) {
      // If the view is an array put all views into insert mode.
      if (_.isArray(view)) {
        return _.each(view, function(view) {
          this.insertView(name, view);
        }, this);
      }

      // Assign each view using the view function.
      this.setView(name, view);
    }, this);

    // Allow for chaining
    return this;
  },

  // By default this should find all nested views and render them into
  // the this.el and call done once all of them have successfully been
  // resolved.
  //
  // This function returns a promise that can be chained to determine
  // once all subviews and main view have been rendered into the view.el.
  render: function() {
    var root = this;
    var options = root.getAllOptions();
    var manager = root.__manager__;
    var parent = manager.parent;
    var rentManager = parent && parent.__manager__;
    var def = options.deferred();

    // Triggered once the render has succeeded.
    function resolve() {
      var next;

      // Insert all subViews into the parent at once.
      _.each(root.views, function(views, selector) {
        // Fragments aren't used on arrays of subviews.
        if (_.isArray(views)) {
          options.htmlBatch(root, views, selector);
        }
      });

      // If there is a parent and we weren't attached to it via the previous
      // method (single view), attach.
      if (parent && !manager.insertedViaFragment) {
        if (!options.contains(parent.el, root.el)) {
          // Apply the partial using parent's html() method.
          parent.getAllOptions().partial(parent.$el, root.$el, rentManager,
            manager);
        }
      }

      // Ensure events are always correctly bound after rendering.
      root.delegateEvents();

      // Set this View as successfully rendered.
      root.hasRendered = true;

      // Only process the queue if it exists.
      if (next = manager.queue.shift()) {
        // Ensure that the next render is only called after all other
        // `done` handlers have completed.  This will prevent `render`
        // callbacks from firing out of order.
        next();
      } else {
        // Once the queue is depleted, remove it, the render process has
        // completed.
        delete manager.queue;
      }

      // Reusable function for triggering the afterRender callback and event
      // and setting the hasRendered flag.
      function completeRender() {
        var console = window.console;
        var afterRender = options.afterRender;

        if (afterRender) {
          afterRender.call(root, root);
        }

        // Always emit an afterRender event.
        root.trigger("afterRender", root);

        // If there are multiple top level elements and `el: false` is used,
        // display a warning message and a stack trace.
        if (manager.noel && root.$el.length > 1) {
          // Do not display a warning while testing or if warning suppression
          // is enabled.
          if (_.isFunction(console.warn) && !options.suppressWarnings) {
            console.warn("`el: false` with multiple top level elements is " +
              "not supported.");

            // Provide a stack trace if available to aid with debugging.
            if (_.isFunction(console.trace)) {
              console.trace();
            }
          }
        }
      }

      // If the parent is currently rendering, wait until it has completed
      // until calling the nested View's `afterRender`.
      if (rentManager && rentManager.queue) {
        // Wait until the parent View has finished rendering, which could be
        // asynchronous, and trigger afterRender on this View once it has
        // compeleted.
        parent.once("afterRender", completeRender);
      } else {
        // This View and its parent have both rendered.
        completeRender();
      }

      return def.resolveWith(root, [root]);
    }

    // Actually facilitate a render.
    function actuallyRender() {
      var options = root.getAllOptions();

      // The `_viewRender` method is broken out to abstract away from having
      // too much code in `actuallyRender`.
      root._render(options).done(function() {
        // If there are no children to worry about, complete the render
        // instantly.
        if (!_.keys(root.views).length) {
          return resolve();
        }

        // Create a list of promises to wait on until rendering is done.
        // Since this method will run on all children as well, its sufficient
        // for a full hierarchical.
        var promises = _.map(root.views, function(view) {
          var insert = _.isArray(view);

          // If items are being inserted, they will be in a non-zero length
          // Array.
          if (insert && view.length) {
            // Mark each subview's manager so they don't attempt to attach by
            // themselves.  Return a single promise representing the entire
            // render.
            return options.when(_.map(view, function(subView) {
              subView.__manager__.insertedViaFragment = true;
              return subView.render().__manager__.renderDeferred;
            }));
          }

          // Only return the fetch deferred, resolve the main deferred after
          // the element has been attached to it's parent.
          return !insert ? view.render().__manager__.renderDeferred : view;
        });

        // Once all nested Views have been rendered, resolve this View's
        // deferred.
        options.when(promises).done(resolve);
      });
    }

    // Another render is currently happening if there is an existing queue, so
    // push a closure to render later into the queue.
    if (manager.queue) {
      aPush.call(manager.queue, actuallyRender);
    } else {
      manager.queue = [];

      // This the first `render`, preceeding the `queue` so render
      // immediately.
      actuallyRender(root, def);
    }

    // Put the deferred inside of the `__manager__` object, since we don't want
    // end users accessing this directly anymore in favor of the `afterRender`
    // event.  So instead of doing `render().then(...` do
    // `render().once("afterRender", ...`.
    root.__manager__.renderDeferred = def;

    // Return the actual View for chainability purposes.
    return root;
  },

  // Ensure the cleanup function is called whenever remove is called.
  remove: function() {
    // Force remove itself from its parent.
    LayoutManager._removeView(this, true);

    // Call the original remove function.
    return this._remove.apply(this, arguments);
  },

  // Merge instance and global options.
  getAllOptions: function() {
    // Instance overrides take precedence, fallback to prototype options.
    return _.extend({}, this, LayoutManager.prototype.options, this.options);
  }
},
{
  // Clearable cache.
  _cache: {},

  // Remove all nested Views.
  _removeViews: function(root, force) {
    // Shift arguments around.
    if (typeof root === "boolean") {
      force = root;
      root = this;
    }

    // Allow removeView to be called on instances.
    root = root || this;

    // Iterate over all of the nested View's and remove.
    root.getViews().each(function(view) {
      // Force doesn't care about if a View has rendered or not.
      if (view.hasRendered || force) {
        LayoutManager._removeView(view, force);
      }
    });
  },

  // Remove a single nested View.
  _removeView: function(view, force) {
    var parentViews;
    // Shorthand the managers for easier access.
    var manager = view.__manager__;
    var rentManager = manager.parent && manager.parent.__manager__;
    // Test for keep.
    var keep = typeof view.keep === "boolean" ? view.keep : view.options.keep;

    // In insert mode, remove views that do not have `keep` attribute set,
    // unless the force flag is set.
    if ((!keep && rentManager && rentManager.insert === true) || force) {
      // Clean out the events.
      LayoutManager.cleanViews(view);

      // Since we are removing this view, force subviews to remove
      view._removeViews(true);

      // Remove the View completely.
      view.$el.remove();

      // Bail out early if no parent exists.
      if (!manager.parent) { return; }

      // Assign (if they exist) the sibling Views to a property.
      parentViews = manager.parent.views[manager.selector];

      // If this is an array of items remove items that are not marked to
      // keep.
      if (_.isArray(parentViews)) {
        // Remove duplicate Views.
        return _.each(_.clone(parentViews), function(view, i) {
          // If the managers match, splice off this View.
          if (view && view.__manager__ === manager) {
            aSplice.call(parentViews, i, 1);
          }
        });
      }

      // Otherwise delete the parent selector.
      delete manager.parent.views[manager.selector];
    }
  },

  // Cache templates into LayoutManager._cache.
  cache: function(path, contents) {
    // If template path is found in the cache, return the contents.
    if (path in this._cache && contents == null) {
      return this._cache[path];
    // Ensure path and contents aren't undefined.
    } else if (path != null && contents != null) {
      return this._cache[path] = contents;
    }

    // If the template is not in the cache, return undefined.
  },

  // Accept either a single view or an array of views to clean of all DOM
  // events internal model and collection references and all Backbone.Events.
  cleanViews: function(views) {
    // Clear out all existing views.
    _.each(aConcat.call([], views), function(view) {
      var cleanup;

      // Remove all custom events attached to this View.
      view.unbind();

      // Automatically unbind `model`.
      if (view.model instanceof Backbone.Model) {
        view.model.off(null, null, view);
      }

      // Automatically unbind `collection`.
      if (view.collection instanceof Backbone.Collection) {
        view.collection.off(null, null, view);
      }

      // Automatically unbind events bound to this View.
      view.stopListening();

      // If a custom cleanup method was provided on the view, call it after
      // the initial cleanup is done
      cleanup = view.getAllOptions().cleanup;
      if (_.isFunction(cleanup)) {
        cleanup.call(view);
      }
    });
  },

  // This static method allows for global configuration of LayoutManager.
  configure: function(options) {
    _.extend(LayoutManager.prototype.options, options);

    // Allow LayoutManager to manage Backbone.View.prototype.
    if (options.manage) {
      Backbone.View.prototype.manage = true;
    }

    // Disable the element globally.
    if (options.el === false) {
      Backbone.View.prototype.el = false;
    }

    // Allow global configuration of `suppressWarnings`.
    if (options.suppressWarnings === true) {
      Backbone.View.prototype.suppressWarnings = true;
    }
  },

  // Configure a View to work with the LayoutManager plugin.
  setupView: function(views, options) {
    // Set up all Views passed.
    _.each(aConcat.call([], views), function(view) {
      // If the View has already been setup, no need to do it again.
      if (view.__manager__) {
        return;
      }

      var views, declaredViews, viewOptions;
      var proto = LayoutManager.prototype;
      var viewOverrides = _.pick(view, keys);

      // Ensure necessary properties are set.
      _.defaults(view, {
        // Ensure a view always has a views object.
        views: {},

        // Ensure a view always has a sections object.
        sections: {},

        // Internal state object used to store whether or not a View has been
        // taken over by layout manager and if it has been rendered into the
        // DOM.
        __manager__: {},

        // Add the ability to remove all Views.
        _removeViews: LayoutManager._removeViews,

        // Add the ability to remove itself.
        _removeView: LayoutManager._removeView

      // Mix in all LayoutManager prototype properties as well.
      }, LayoutManager.prototype);

      // Extend the options with the prototype and passed options.
      options = view.options = _.defaults(options || {}, view.options,
        proto.options);

      // Ensure view events are properly copied over.
      viewOptions = _.pick(options, aConcat.call(["events", "sections"],
        _.values(options.events || {})));

      // Merge the View options into the View.
      _.extend(view, viewOptions);

      // Pick out the specific properties that can be dynamically added at
      // runtime and ensure they are available on the view object.
      _.extend(options, viewOverrides);

      // By default the original Remove function is the Backbone.View one.
      view._remove = Backbone.View.prototype.remove;

      // Ensure the render is always set correctly.
      view.render = LayoutManager.prototype.render;

      // If the user provided their own remove override, use that instead of
      // the default.
      if (view.remove !== proto.remove) {
        view._remove = view.remove;
        view.remove = proto.remove;
      }

      // Normalize views to exist on either instance or options, default to
      // options.
      views = options.views || view.views;

      // Set the internal views, only if selectors have been provided.
      if (_.keys(views).length) {
        // Keep original object declared containing Views.
        declaredViews = views;

        // Reset the property to avoid duplication or overwritting.
        view.views = {};

        // If any declared view is wrapped in a function, invoke it.
        _.each(declaredViews, function(declaredView, key) {
          if (typeof declaredView === "function") {
            declaredViews[key] = declaredView.call(view, view);
          }
        });

        // Set the declared Views.
        view.setViews(declaredViews);
      }

      // If a template is passed use that instead.
      if (view.options.template) {
        view.options.template = options.template;
      // Ensure the template is mapped over.
      } else if (view.template) {
        options.template = view.template;
      }
    });
  }
});

// Tack on the version.
LayoutManager.VERSION = "0.9.3";

Backbone.Layout = LayoutManager;

// Override _configure to provide extra functionality that is necessary in
// order for the render function reference to be bound during initialize.
Backbone.View.prototype._configure = function(options) {
  var noel, retVal;

  // Remove the container element provided by Backbone.
  if ("el" in options ? options.el === false : this.el === false) {
    noel = true;
  }

  // Run the original _configure.
  retVal = _configure.apply(this, arguments);

  // If manage is set, do it!
  if (options.manage || this.manage) {
    // Set up this View.
    LayoutManager.setupView(this);
  }

  // Assign the `noel` property once we're sure the View we're working with is
  // managed by LayoutManager.
  if (this.__manager__) {
    this.__manager__.noel = noel;
    this.__manager__.suppressWarnings = options.suppressWarnings;
  }

  // Act like nothing happened.
  return retVal;
};

// Default configuration options; designed to be overriden.
LayoutManager.prototype.options = {
  // Prefix template/layout paths.
  prefix: "",

  // Can be used to supply a different deferred implementation.
  deferred: function() {
    return $.Deferred();
  },

  // Fetch is passed a path and is expected to return template contents as a
  // function or string.
  fetchTemplate: function(path) {
    return _.template($(path).html());
  },

  // By default, render using underscore's templating and trim output.
  renderTemplate: function(template, context) {
    return trim(template(context));
  },

  // By default, pass model attributes to the templates
  serialize: function() {
    return this.model ? _.clone(this.model.attributes) : {};
  },

  // This is the most common way you will want to partially apply a view into
  // a layout.
  partial: function($root, $el, rentManager, manager) {
    var $filtered;

    // If selector is specified, attempt to find it.
    if (manager.selector) {
      if (rentManager.noel) {
        $filtered = $root.filter(manager.selector);
        $root = $filtered.length ? $filtered : $root.find(manager.selector);
      } else {
        $root = $root.find(manager.selector);
      }
    }

    // Use the insert method if the parent's `insert` argument is true.
    if (rentManager.insert) {
      this.insert($root, $el);
    } else {
      this.html($root, $el);
    }
  },

  // Override this with a custom HTML method, passed a root element and content
  // (a jQuery collection or a string) to replace the innerHTML with.
  html: function($root, content) {
    $root.html(content);
  },

  // Used for inserting subViews in a single batch.  This gives a small
  // performance boost as we write to a disconnected fragment instead of to the
  // DOM directly. Smarter browsers like Chrome will batch writes internally
  // and layout as seldom as possible, but even in that case this provides a
  // decent boost.  jQuery will use a DocumentFragment for the batch update,
  // but Cheerio in Node will not.
  htmlBatch: function(rootView, subViews, selector) {
    // Shorthand the parent manager object.
    var rentManager = rootView.__manager__;
    // Create a simplified manager object that tells partial() where
    // place the elements.
    var manager = { selector: selector };

    // Get the elements to be inserted into the root view.
    var els = _.reduce(subViews, function(memo, sub) {
      // Check if keep is present - do boolean check in case the user
      // has created a `keep` function.
      var keep = typeof sub.keep === "boolean" ? sub.keep : sub.options.keep;
      // If a subView is present, don't push it.  This can only happen if
      // `keep: true`.  We do the keep check for speed as $.contains is not
      // cheap.
      var exists = keep && $.contains(rootView.el, sub.el);

      // If there is an element and it doesn't already exist in our structure
      // attach it.
      if (sub.el && !exists) {
        memo.push(sub.el);
      }

      return memo;
    }, []);

    // Use partial to apply the elements. Wrap els in jQ obj for cheerio.
    return this.partial(rootView.$el, $(els), rentManager, manager);
  },

  // Very similar to HTML except this one will appendChild by default.
  insert: function($root, $el) {
    $root.append($el);
  },

  // Return a deferred for when all promises resolve/reject.
  when: function(promises) {
    return $.when.apply(null, promises);
  },

  // A method to determine if a View contains another.
  contains: function(parent, child) {
    return $.contains(parent, child);
  }
};

// Maintain a list of the keys at define time.
keys = _.keys(LayoutManager.prototype.options);

// Assign `LayoutManager` object for AMD loaders.
return LayoutManager;

}));