ReactDOMComponent.js

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactDOMComponent
 */

/* global hasOwnProperty:true */

'use strict';

var AutoFocusUtils = require('AutoFocusUtils');
var CSSPropertyOperations = require('CSSPropertyOperations');
var DOMLazyTree = require('DOMLazyTree');
var DOMNamespaces = require('DOMNamespaces');
var DOMProperty = require('DOMProperty');
var DOMPropertyOperations = require('DOMPropertyOperations');
var EventPluginHub = require('EventPluginHub');
var EventPluginRegistry = require('EventPluginRegistry');
var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
var ReactDOMComponentFlags = require('ReactDOMComponentFlags');
var ReactDOMComponentTree = require('ReactDOMComponentTree');
var ReactDOMInput = require('ReactDOMInput');
var ReactDOMOption = require('ReactDOMOption');
var ReactDOMSelect = require('ReactDOMSelect');
var ReactDOMTextarea = require('ReactDOMTextarea');
var ReactInstrumentation = require('ReactInstrumentation');
var ReactMultiChild = require('ReactMultiChild');
var ReactServerRenderingTransaction = require('ReactServerRenderingTransaction');

var emptyFunction = require('emptyFunction');
var escapeTextContentForBrowser = require('escapeTextContentForBrowser');
var invariant = require('invariant');
var isEventSupported = require('isEventSupported');
var shallowEqual = require('shallowEqual');
var inputValueTracking = require('inputValueTracking');
var validateDOMNesting = require('validateDOMNesting');
var warning = require('warning');

var Flags = ReactDOMComponentFlags;
var deleteListener = EventPluginHub.deleteListener;
var getNode = ReactDOMComponentTree.getNodeFromInstance;
var listenTo = ReactBrowserEventEmitter.listenTo;
var registrationNameModules = EventPluginRegistry.registrationNameModules;

// For quickly matching children type, to test if can be treated as content.
var CONTENT_TYPES = {'string': true, 'number': true};

var STYLE = 'style';
var HTML = '__html';
var RESERVED_PROPS = {
  children: null,
  dangerouslySetInnerHTML: null,
  suppressContentEditableWarning: null,
};

// Node type for document fragments (Node.DOCUMENT_FRAGMENT_NODE).
var DOC_FRAGMENT_TYPE = 11;


function getDeclarationErrorAddendum(internalInstance) {
  if (internalInstance) {
    var owner = internalInstance._currentElement._owner || null;
    if (owner) {
      var name = owner.getName();
      if (name) {
        return ' This DOM node was rendered by `' + name + '`.';
      }
    }
  }
  return '';
}

function friendlyStringify(obj) {
  if (typeof obj === 'object') {
    if (Array.isArray(obj)) {
      return '[' + obj.map(friendlyStringify).join(', ') + ']';
    } else {
      var pairs = [];
      for (var key in obj) {
        if (Object.prototype.hasOwnProperty.call(obj, key)) {
          var keyEscaped = /^[a-z$_][\w$_]*$/i.test(key) ?
            key :
            JSON.stringify(key);
          pairs.push(keyEscaped + ': ' + friendlyStringify(obj[key]));
        }
      }
      return '{' + pairs.join(', ') + '}';
    }
  } else if (typeof obj === 'string') {
    return JSON.stringify(obj);
  } else if (typeof obj === 'function') {
    return '[function object]';
  }
  // Differs from JSON.stringify in that undefined because undefined and that
  // inf and nan don't become null
  return String(obj);
}

var styleMutationWarning = {};

function checkAndWarnForMutatedStyle(style1, style2, component) {
  if (style1 == null || style2 == null) {
    return;
  }
  if (shallowEqual(style1, style2)) {
    return;
  }

  var componentName = component._tag;
  var owner = component._currentElement._owner;
  var ownerName;
  if (owner) {
    ownerName = owner.getName();
  }

  var hash = ownerName + '|' + componentName;

  if (styleMutationWarning.hasOwnProperty(hash)) {
    return;
  }

  styleMutationWarning[hash] = true;

  warning(
    false,
    '`%s` was passed a style object that has previously been mutated. ' +
    'Mutating `style` is deprecated. Consider cloning it beforehand. Check ' +
    'the `render` %s. Previous style: %s. Mutated style: %s.',
    componentName,
    owner ? 'of `' + ownerName + '`' : 'using <' + componentName + '>',
    friendlyStringify(style1),
    friendlyStringify(style2)
  );
}

/**
 * @param {object} component
 * @param {?object} props
 */
function assertValidProps(component, props) {
  if (!props) {
    return;
  }
  // Note the use of `==` which checks for null or undefined.
  if (voidElementTags[component._tag]) {
    invariant(
      props.children == null && props.dangerouslySetInnerHTML == null,
      '%s is a void element tag and must neither have `children` nor ' +
      'use `dangerouslySetInnerHTML`.%s',
      component._tag,
      component._currentElement._owner ?
        ' Check the render method of ' +
        component._currentElement._owner.getName() + '.' :
        ''
    );
  }
  if (props.dangerouslySetInnerHTML != null) {
    invariant(
      props.children == null,
      'Can only set one of `children` or `props.dangerouslySetInnerHTML`.'
    );
    invariant(
      typeof props.dangerouslySetInnerHTML === 'object' &&
      HTML in props.dangerouslySetInnerHTML,
      '`props.dangerouslySetInnerHTML` must be in the form `{__html: ...}`. ' +
      'Please visit https://fb.me/react-invariant-dangerously-set-inner-html ' +
      'for more information.'
    );
  }
  if (__DEV__) {
    warning(
      props.innerHTML == null,
      'Directly setting property `innerHTML` is not permitted. ' +
      'For more information, lookup documentation on `dangerouslySetInnerHTML`.'
    );
    warning(
      props.suppressContentEditableWarning ||
      !props.contentEditable ||
      props.children == null,
      'A component is `contentEditable` and contains `children` managed by ' +
      'React. It is now your responsibility to guarantee that none of ' +
      'those nodes are unexpectedly modified or duplicated. This is ' +
      'probably not intentional.'
    );
    warning(
      props.onFocusIn == null &&
      props.onFocusOut == null,
      'React uses onFocus and onBlur instead of onFocusIn and onFocusOut. ' +
      'All React events are normalized to bubble, so onFocusIn and onFocusOut ' +
      'are not needed/supported by React.'
    );
  }
  invariant(
    props.style == null || typeof props.style === 'object',
    'The `style` prop expects a mapping from style properties to values, ' +
    'not a string. For example, style={{marginRight: spacing + \'em\'}} when ' +
    'using JSX.%s',
     getDeclarationErrorAddendum(component)
  );
}

function enqueuePutListener(inst, registrationName, listener, transaction) {
  if (transaction instanceof ReactServerRenderingTransaction) {
    return;
  }
  if (__DEV__) {
    // IE8 has no API for event capturing and the `onScroll` event doesn't
    // bubble.
    warning(
      registrationName !== 'onScroll' || isEventSupported('scroll', true),
      'This browser doesn\'t support the `onScroll` event'
    );
  }
  var containerInfo = inst._hostContainerInfo;
  var isDocumentFragment = containerInfo._node && containerInfo._node.nodeType === DOC_FRAGMENT_TYPE;
  var doc = isDocumentFragment ? containerInfo._node : containerInfo._ownerDocument;
  listenTo(registrationName, doc);
  transaction.getReactMountReady().enqueue(putListener, {
    inst: inst,
    registrationName: registrationName,
    listener: listener,
  });
}

function putListener() {
  var listenerToPut = this;
  EventPluginHub.putListener(
    listenerToPut.inst,
    listenerToPut.registrationName,
    listenerToPut.listener
  );
}

function inputPostMount() {
  var inst = this;
  ReactDOMInput.postMountWrapper(inst);
}

function textareaPostMount() {
  var inst = this;
  ReactDOMTextarea.postMountWrapper(inst);
}

function optionPostMount() {
  var inst = this;
  ReactDOMOption.postMountWrapper(inst);
}

var setAndValidateContentChildDev = emptyFunction;
if (__DEV__) {
  setAndValidateContentChildDev = function(content) {
    var hasExistingContent = this._contentDebugID != null;
    var debugID = this._debugID;
    // This ID represents the inlined child that has no backing instance:
    var contentDebugID = -debugID;

    if (content == null) {
      if (hasExistingContent) {
        ReactInstrumentation.debugTool.onUnmountComponent(this._contentDebugID);
      }
      this._contentDebugID = null;
      return;
    }

    validateDOMNesting(null, String(content), this, this._ancestorInfo);
    this._contentDebugID = contentDebugID;
    if (hasExistingContent) {
      ReactInstrumentation.debugTool.onBeforeUpdateComponent(contentDebugID, content);
      ReactInstrumentation.debugTool.onUpdateComponent(contentDebugID);
    } else {
      ReactInstrumentation.debugTool.onBeforeMountComponent(contentDebugID, content, debugID);
      ReactInstrumentation.debugTool.onMountComponent(contentDebugID);
      ReactInstrumentation.debugTool.onSetChildren(debugID, [contentDebugID]);
    }
  };
}

// There are so many media events, it makes sense to just
// maintain a list rather than create a `trapBubbledEvent` for each
var mediaEvents = {
  topAbort: 'abort',
  topCanPlay: 'canplay',
  topCanPlayThrough: 'canplaythrough',
  topDurationChange: 'durationchange',
  topEmptied: 'emptied',
  topEncrypted: 'encrypted',
  topEnded: 'ended',
  topError: 'error',
  topLoadedData: 'loadeddata',
  topLoadedMetadata: 'loadedmetadata',
  topLoadStart: 'loadstart',
  topPause: 'pause',
  topPlay: 'play',
  topPlaying: 'playing',
  topProgress: 'progress',
  topRateChange: 'ratechange',
  topSeeked: 'seeked',
  topSeeking: 'seeking',
  topStalled: 'stalled',
  topSuspend: 'suspend',
  topTimeUpdate: 'timeupdate',
  topVolumeChange: 'volumechange',
  topWaiting: 'waiting',
};

function trackInputValue() {
  inputValueTracking.track(this);
}

function trapBubbledEventsLocal() {
  var inst = this;
  // If a component renders to null or if another component fatals and causes
  // the state of the tree to be corrupted, `node` here can be null.
  invariant(inst._rootNodeID, 'Must be mounted to trap events');
  var node = getNode(inst);
  invariant(
    node,
    'trapBubbledEvent(...): Requires node to be rendered.'
  );

  switch (inst._tag) {
    case 'iframe':
    case 'object':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topLoad',
          'load',
          node
        ),
      ];
      break;
    case 'video':
    case 'audio':

      inst._wrapperState.listeners = [];
      // Create listener for each media event
      for (var event in mediaEvents) {
        if (mediaEvents.hasOwnProperty(event)) {
          inst._wrapperState.listeners.push(
            ReactBrowserEventEmitter.trapBubbledEvent(
              event,
              mediaEvents[event],
              node
            )
          );
        }
      }
      break;
    case 'source':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topError',
          'error',
          node
        ),
      ];
      break;
    case 'img':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topError',
          'error',
          node
        ),
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topLoad',
          'load',
          node
        ),
      ];
      break;
    case 'form':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topReset',
          'reset',
          node
        ),
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topSubmit',
          'submit',
          node
        ),
      ];
      break;
    case 'input':
    case 'select':
    case 'textarea':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topInvalid',
          'invalid',
          node
        ),
      ];
      break;
  }
}

function postUpdateSelectWrapper() {
  ReactDOMSelect.postUpdateWrapper(this);
}

// For HTML, certain tags should omit their close tag. We keep a whitelist for
// those special-case tags.

var omittedCloseTags = {
  'area': true,
  'base': true,
  'br': true,
  'col': true,
  'embed': true,
  'hr': true,
  'img': true,
  'input': true,
  'keygen': true,
  'link': true,
  'meta': true,
  'param': true,
  'source': true,
  'track': true,
  'wbr': true,
  // NOTE: menuitem's close tag should be omitted, but that causes problems.
};

var newlineEatingTags = {
  'listing': true,
  'pre': true,
  'textarea': true,
};

// For HTML, certain tags cannot have children. This has the same purpose as
// `omittedCloseTags` except that `menuitem` should still have its closing tag.

var voidElementTags = Object.assign({
  'menuitem': true,
}, omittedCloseTags);

// We accept any tag to be rendered but since this gets injected into arbitrary
// HTML, we want to make sure that it's a safe tag.
// http://www.w3.org/TR/REC-xml/#NT-Name

var VALID_TAG_REGEX = /^[a-zA-Z][a-zA-Z:_\.\-\d]*$/; // Simplified subset
var validatedTagCache = {};
var hasOwnProperty = {}.hasOwnProperty;

function validateDangerousTag(tag) {
  if (!hasOwnProperty.call(validatedTagCache, tag)) {
    invariant(VALID_TAG_REGEX.test(tag), 'Invalid tag: %s', tag);
    validatedTagCache[tag] = true;
  }
}

function isCustomComponent(tagName, props) {
  return tagName.indexOf('-') >= 0 || props.is != null;
}

var globalIdCounter = 1;

/**
 * Creates a new React class that is idempotent and capable of containing other
 * React components. It accepts event listeners and DOM properties that are
 * valid according to `DOMProperty`.
 *
 *  - Event listeners: `onClick`, `onMouseDown`, etc.
 *  - DOM properties: `className`, `name`, `title`, etc.
 *
 * The `style` property functions differently from the DOM API. It accepts an
 * object mapping of style properties to values.
 *
 * @constructor ReactDOMComponent
 * @extends ReactMultiChild
 */
function ReactDOMComponent(element) {
  var tag = element.type;
  validateDangerousTag(tag);
  this._currentElement = element;
  this._tag = tag.toLowerCase();
  this._namespaceURI = null;
  this._renderedChildren = null;
  this._previousStyle = null;
  this._previousStyleCopy = null;
  this._hostNode = null;
  this._hostParent = null;
  this._rootNodeID = 0;
  this._domID = 0;
  this._hostContainerInfo = null;
  this._wrapperState = null;
  this._topLevelWrapper = null;
  this._flags = 0;
  if (__DEV__) {
    this._ancestorInfo = null;
    setAndValidateContentChildDev.call(this, null);
  }
}

ReactDOMComponent.displayName = 'ReactDOMComponent';

ReactDOMComponent.Mixin = {

  /**
   * Generates root tag markup then recurses. This method has side effects and
   * is not idempotent.
   *
   * @internal
   * @param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
   * @param {?ReactDOMComponent} the parent component instance
   * @param {?object} info about the host container
   * @param {object} context
   * @return {string} The computed markup.
   */
  mountComponent: function(
    transaction,
    hostParent,
    hostContainerInfo,
    context
  ) {
    this._rootNodeID = globalIdCounter++;
    this._domID = hostContainerInfo._idCounter++;
    this._hostParent = hostParent;
    this._hostContainerInfo = hostContainerInfo;

    var props = this._currentElement.props;

    switch (this._tag) {
      case 'audio':
      case 'form':
      case 'iframe':
      case 'img':
      case 'link':
      case 'object':
      case 'source':
      case 'video':
        this._wrapperState = {
          listeners: null,
        };
        transaction.getReactMountReady().enqueue(trapBubbledEventsLocal, this);
        break;
      case 'input':
        ReactDOMInput.mountWrapper(this, props, hostParent);
        props = ReactDOMInput.getHostProps(this, props);
        transaction.getReactMountReady().enqueue(trackInputValue, this);
        transaction.getReactMountReady().enqueue(trapBubbledEventsLocal, this);
        break;
      case 'option':
        ReactDOMOption.mountWrapper(this, props, hostParent);
        props = ReactDOMOption.getHostProps(this, props);
        break;
      case 'select':
        ReactDOMSelect.mountWrapper(this, props, hostParent);
        props = ReactDOMSelect.getHostProps(this, props);
        transaction.getReactMountReady().enqueue(trapBubbledEventsLocal, this);
        break;
      case 'textarea':
        ReactDOMTextarea.mountWrapper(this, props, hostParent);
        props = ReactDOMTextarea.getHostProps(this, props);
        transaction.getReactMountReady().enqueue(trackInputValue, this);
        transaction.getReactMountReady().enqueue(trapBubbledEventsLocal, this);
        break;
    }

    assertValidProps(this, props);

    // We create tags in the namespace of their parent container, except HTML
    // tags get no namespace.
    var namespaceURI;
    var parentTag;
    if (hostParent != null) {
      namespaceURI = hostParent._namespaceURI;
      parentTag = hostParent._tag;
    } else if (hostContainerInfo._tag) {
      namespaceURI = hostContainerInfo._namespaceURI;
      parentTag = hostContainerInfo._tag;
    }
    if (namespaceURI == null ||
        namespaceURI === DOMNamespaces.svg && parentTag === 'foreignobject') {
      namespaceURI = DOMNamespaces.html;
    }
    if (namespaceURI === DOMNamespaces.html) {
      if (this._tag === 'svg') {
        namespaceURI = DOMNamespaces.svg;
      } else if (this._tag === 'math') {
        namespaceURI = DOMNamespaces.mathml;
      }
    }
    this._namespaceURI = namespaceURI;

    if (__DEV__) {
      var parentInfo;
      if (hostParent != null) {
        parentInfo = hostParent._ancestorInfo;
      } else if (hostContainerInfo._tag) {
        parentInfo = hostContainerInfo._ancestorInfo;
      }
      if (parentInfo) {
        // parentInfo should always be present except for the top-level
        // component when server rendering
        validateDOMNesting(this._tag, null, this, parentInfo);
      }
      this._ancestorInfo =
        validateDOMNesting.updatedAncestorInfo(parentInfo, this._tag, this);
    }

    var mountImage;
    if (transaction.useCreateElement) {
      var ownerDocument = hostContainerInfo._ownerDocument;
      var el;
      if (namespaceURI === DOMNamespaces.html) {
        if (this._tag === 'script') {
          // Create the script via .innerHTML so its "parser-inserted" flag is
          // set to true and it does not execute
          var div = ownerDocument.createElement('div');
          var type = this._currentElement.type;
          div.innerHTML = `<${type}></${type}>`;
          el = div.removeChild(div.firstChild);
        } else if (props.is) {
          el = ownerDocument.createElement(this._currentElement.type, props.is);
        } else {
          // Separate else branch instead of using `props.is || undefined` above becuase of a Firefox bug.
          // See discussion in https://github.com/facebook/react/pull/6896
          // and discussion in https://bugzilla.mozilla.org/show_bug.cgi?id=1276240
          el = ownerDocument.createElement(this._currentElement.type);
        }
      } else {
        el = ownerDocument.createElementNS(
          namespaceURI,
          this._currentElement.type
        );
      }
      ReactDOMComponentTree.precacheNode(this, el);
      this._flags |= Flags.hasCachedChildNodes;
      if (!this._hostParent) {
        DOMPropertyOperations.setAttributeForRoot(el);
      }
      this._updateDOMProperties(null, props, transaction);
      var lazyTree = DOMLazyTree(el);
      this._createInitialChildren(transaction, props, context, lazyTree);
      mountImage = lazyTree;
    } else {
      var tagOpen = this._createOpenTagMarkupAndPutListeners(transaction, props);
      var tagContent = this._createContentMarkup(transaction, props, context);
      if (!tagContent && omittedCloseTags[this._tag]) {
        mountImage = tagOpen + '/>';
      } else {
        mountImage =
          tagOpen + '>' + tagContent + '</' + this._currentElement.type + '>';
      }
    }

    switch (this._tag) {
      case 'input':
        transaction.getReactMountReady().enqueue(
          inputPostMount,
          this
        );
        if (props.autoFocus) {
          transaction.getReactMountReady().enqueue(
            AutoFocusUtils.focusDOMComponent,
            this
          );
        }
        break;
      case 'textarea':
        transaction.getReactMountReady().enqueue(
          textareaPostMount,
          this
        );
        if (props.autoFocus) {
          transaction.getReactMountReady().enqueue(
            AutoFocusUtils.focusDOMComponent,
            this
          );
        }
        break;
      case 'select':
        if (props.autoFocus) {
          transaction.getReactMountReady().enqueue(
            AutoFocusUtils.focusDOMComponent,
            this
          );
        }
        break;
      case 'button':
        if (props.autoFocus) {
          transaction.getReactMountReady().enqueue(
            AutoFocusUtils.focusDOMComponent,
            this
          );
        }
        break;
      case 'option':
        transaction.getReactMountReady().enqueue(
          optionPostMount,
          this
        );
        break;
    }

    return mountImage;
  },

  /**
   * Creates markup for the open tag and all attributes.
   *
   * This method has side effects because events get registered.
   *
   * Iterating over object properties is faster than iterating over arrays.
   * @see http://jsperf.com/obj-vs-arr-iteration
   *
   * @private
   * @param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
   * @param {object} props
   * @return {string} Markup of opening tag.
   */
  _createOpenTagMarkupAndPutListeners: function(transaction, props) {
    var ret = '<' + this._currentElement.type;

    for (var propKey in props) {
      if (!props.hasOwnProperty(propKey)) {
        continue;
      }
      var propValue = props[propKey];
      if (propValue == null) {
        continue;
      }
      if (registrationNameModules.hasOwnProperty(propKey)) {
        if (propValue) {
          enqueuePutListener(this, propKey, propValue, transaction);
        }
      } else {
        if (propKey === STYLE) {
          if (propValue) {
            if (__DEV__) {
              // See `_updateDOMProperties`. style block
              this._previousStyle = propValue;
            }
            propValue = this._previousStyleCopy = Object.assign({}, props.style);
          }
          propValue = CSSPropertyOperations.createMarkupForStyles(propValue, this);
        }
        var markup = null;
        if (this._tag != null && isCustomComponent(this._tag, props)) {
          if (!RESERVED_PROPS.hasOwnProperty(propKey)) {
            markup = DOMPropertyOperations.createMarkupForCustomAttribute(propKey, propValue);
          }
        } else {
          markup = DOMPropertyOperations.createMarkupForProperty(propKey, propValue);
        }
        if (markup) {
          ret += ' ' + markup;
        }
      }
    }

    // For static pages, no need to put React ID and checksum. Saves lots of
    // bytes.
    if (transaction.renderToStaticMarkup) {
      return ret;
    }

    if (!this._hostParent) {
      ret += ' ' + DOMPropertyOperations.createMarkupForRoot();
    }
    ret += ' ' + DOMPropertyOperations.createMarkupForID(this._domID);
    return ret;
  },

  /**
   * Creates markup for the content between the tags.
   *
   * @private
   * @param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
   * @param {object} props
   * @param {object} context
   * @return {string} Content markup.
   */
  _createContentMarkup: function(transaction, props, context) {
    var ret = '';

    // Intentional use of != to avoid catching zero/false.
    var innerHTML = props.dangerouslySetInnerHTML;
    if (innerHTML != null) {
      if (innerHTML.__html != null) {
        ret = innerHTML.__html;
      }
    } else {
      var contentToUse =
        CONTENT_TYPES[typeof props.children] ? props.children : null;
      var childrenToUse = contentToUse != null ? null : props.children;
      if (contentToUse != null) {
        // TODO: Validate that text is allowed as a child of this node
        ret = escapeTextContentForBrowser(contentToUse);
        if (__DEV__) {
          setAndValidateContentChildDev.call(this, contentToUse);
        }
      } else if (childrenToUse != null) {
        var mountImages = this.mountChildren(
          childrenToUse,
          transaction,
          context
        );
        ret = mountImages.join('');
      }
    }
    if (newlineEatingTags[this._tag] && ret.charAt(0) === '\n') {
      // text/html ignores the first character in these tags if it's a newline
      // Prefer to break application/xml over text/html (for now) by adding
      // a newline specifically to get eaten by the parser. (Alternately for
      // textareas, replacing "^\n" with "\r\n" doesn't get eaten, and the first
      // \r is normalized out by HTMLTextAreaElement#value.)
      // See: <http://www.w3.org/TR/html-polyglot/#newlines-in-textarea-and-pre>
      // See: <http://www.w3.org/TR/html5/syntax.html#element-restrictions>
      // See: <http://www.w3.org/TR/html5/syntax.html#newlines>
      // See: Parsing of "textarea" "listing" and "pre" elements
      //  from <http://www.w3.org/TR/html5/syntax.html#parsing-main-inbody>
      return '\n' + ret;
    } else {
      return ret;
    }
  },

  _createInitialChildren: function(transaction, props, context, lazyTree) {
    // Intentional use of != to avoid catching zero/false.
    var innerHTML = props.dangerouslySetInnerHTML;
    if (innerHTML != null) {
      if (innerHTML.__html != null) {
        DOMLazyTree.queueHTML(lazyTree, innerHTML.__html);
      }
    } else {
      var contentToUse =
        CONTENT_TYPES[typeof props.children] ? props.children : null;
      var childrenToUse = contentToUse != null ? null : props.children;
      if (contentToUse != null) {
        // TODO: Validate that text is allowed as a child of this node
        if (__DEV__) {
          setAndValidateContentChildDev.call(this, contentToUse);
        }
        DOMLazyTree.queueText(lazyTree, contentToUse);
      } else if (childrenToUse != null) {
        var mountImages = this.mountChildren(
          childrenToUse,
          transaction,
          context
        );
        for (var i = 0; i < mountImages.length; i++) {
          DOMLazyTree.queueChild(lazyTree, mountImages[i]);
        }
      }
    }
  },

  /**
   * Receives a next element and updates the component.
   *
   * @internal
   * @param {ReactElement} nextElement
   * @param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
   * @param {object} context
   */
  receiveComponent: function(nextElement, transaction, context) {
    var prevElement = this._currentElement;
    this._currentElement = nextElement;
    this.updateComponent(transaction, prevElement, nextElement, context);
  },

  /**
   * Updates a DOM component after it has already been allocated and
   * attached to the DOM. Reconciles the root DOM node, then recurses.
   *
   * @param {ReactReconcileTransaction} transaction
   * @param {ReactElement} prevElement
   * @param {ReactElement} nextElement
   * @internal
   * @overridable
   */
  updateComponent: function(transaction, prevElement, nextElement, context) {
    var lastProps = prevElement.props;
    var nextProps = this._currentElement.props;

    switch (this._tag) {
      case 'input':
        lastProps = ReactDOMInput.getHostProps(this, lastProps);
        nextProps = ReactDOMInput.getHostProps(this, nextProps);
        break;
      case 'option':
        lastProps = ReactDOMOption.getHostProps(this, lastProps);
        nextProps = ReactDOMOption.getHostProps(this, nextProps);
        break;
      case 'select':
        lastProps = ReactDOMSelect.getHostProps(this, lastProps);
        nextProps = ReactDOMSelect.getHostProps(this, nextProps);
        break;
      case 'textarea':
        lastProps = ReactDOMTextarea.getHostProps(this, lastProps);
        nextProps = ReactDOMTextarea.getHostProps(this, nextProps);
        break;
    }

    assertValidProps(this, nextProps);
    this._updateDOMProperties(lastProps, nextProps, transaction);
    this._updateDOMChildren(
      lastProps,
      nextProps,
      transaction,
      context
    );

    switch (this._tag) {
      case 'input':
        // Update the wrapper around inputs *after* updating props. This has to
        // happen after `_updateDOMProperties`. Otherwise HTML5 input validations
        // raise warnings and prevent the new value from being assigned.
        ReactDOMInput.updateWrapper(this);
        break;
      case 'textarea':
        ReactDOMTextarea.updateWrapper(this);
        break;
      case 'select':
        // <select> value update needs to occur after <option> children
        // reconciliation
        transaction.getReactMountReady().enqueue(postUpdateSelectWrapper, this);
        break;
    }
  },

  /**
   * Reconciles the properties by detecting differences in property values and
   * updating the DOM as necessary. This function is probably the single most
   * critical path for performance optimization.
   *
   * TODO: Benchmark whether checking for changed values in memory actually
   *       improves performance (especially statically positioned elements).
   * TODO: Benchmark the effects of putting this at the top since 99% of props
   *       do not change for a given reconciliation.
   * TODO: Benchmark areas that can be improved with caching.
   *
   * @private
   * @param {object} lastProps
   * @param {object} nextProps
   * @param {?DOMElement} node
   */
  _updateDOMProperties: function(lastProps, nextProps, transaction) {
    var propKey;
    var styleName;
    var styleUpdates;
    for (propKey in lastProps) {
      if (nextProps.hasOwnProperty(propKey) ||
         !lastProps.hasOwnProperty(propKey) ||
         lastProps[propKey] == null) {
        continue;
      }
      if (propKey === STYLE) {
        var lastStyle = this._previousStyleCopy;
        for (styleName in lastStyle) {
          if (lastStyle.hasOwnProperty(styleName)) {
            styleUpdates = styleUpdates || {};
            styleUpdates[styleName] = '';
          }
        }
        this._previousStyleCopy = null;
      } else if (registrationNameModules.hasOwnProperty(propKey)) {
        if (lastProps[propKey]) {
          // Only call deleteListener if there was a listener previously or
          // else willDeleteListener gets called when there wasn't actually a
          // listener (e.g., onClick={null})
          deleteListener(this, propKey);
        }
      } else if (isCustomComponent(this._tag, lastProps)) {
        if (!RESERVED_PROPS.hasOwnProperty(propKey)) {
          DOMPropertyOperations.deleteValueForAttribute(
            getNode(this),
            propKey
          );
        }
      } else if (
          DOMProperty.properties[propKey] ||
          DOMProperty.isCustomAttribute(propKey)) {
        DOMPropertyOperations.deleteValueForProperty(getNode(this), propKey);
      }
    }
    for (propKey in nextProps) {
      var nextProp = nextProps[propKey];
      var lastProp =
        propKey === STYLE ? this._previousStyleCopy :
        lastProps != null ? lastProps[propKey] : undefined;
      if (!nextProps.hasOwnProperty(propKey) ||
          nextProp === lastProp ||
          nextProp == null && lastProp == null) {
        continue;
      }
      if (propKey === STYLE) {
        if (nextProp) {
          if (__DEV__) {
            checkAndWarnForMutatedStyle(
              this._previousStyleCopy,
              this._previousStyle,
              this
            );
            this._previousStyle = nextProp;
          }
          nextProp = this._previousStyleCopy = Object.assign({}, nextProp);
        } else {
          this._previousStyleCopy = null;
        }
        if (lastProp) {
          // Unset styles on `lastProp` but not on `nextProp`.
          for (styleName in lastProp) {
            if (lastProp.hasOwnProperty(styleName) &&
                (!nextProp || !nextProp.hasOwnProperty(styleName))) {
              styleUpdates = styleUpdates || {};
              styleUpdates[styleName] = '';
            }
          }
          // Update styles that changed since `lastProp`.
          for (styleName in nextProp) {
            if (nextProp.hasOwnProperty(styleName) &&
                lastProp[styleName] !== nextProp[styleName]) {
              styleUpdates = styleUpdates || {};
              styleUpdates[styleName] = nextProp[styleName];
            }
          }
        } else {
          // Relies on `updateStylesByID` not mutating `styleUpdates`.
          styleUpdates = nextProp;
        }
      } else if (registrationNameModules.hasOwnProperty(propKey)) {
        if (nextProp) {
          enqueuePutListener(this, propKey, nextProp, transaction);
        } else if (lastProp) {
          deleteListener(this, propKey);
        }
      } else if (isCustomComponent(this._tag, nextProps)) {
        if (!RESERVED_PROPS.hasOwnProperty(propKey)) {
          DOMPropertyOperations.setValueForAttribute(
            getNode(this),
            propKey,
            nextProp
          );
        }
      } else if (
          DOMProperty.properties[propKey] ||
          DOMProperty.isCustomAttribute(propKey)) {
        var node = getNode(this);
        // If we're updating to null or undefined, we should remove the property
        // from the DOM node instead of inadvertently setting to a string. This
        // brings us in line with the same behavior we have on initial render.
        if (nextProp != null) {
          DOMPropertyOperations.setValueForProperty(node, propKey, nextProp);
        } else {
          DOMPropertyOperations.deleteValueForProperty(node, propKey);
        }
      }
    }
    if (styleUpdates) {
      CSSPropertyOperations.setValueForStyles(
        getNode(this),
        styleUpdates,
        this
      );
    }
  },

  /**
   * Reconciles the children with the various properties that affect the
   * children content.
   *
   * @param {object} lastProps
   * @param {object} nextProps
   * @param {ReactReconcileTransaction} transaction
   * @param {object} context
   */
  _updateDOMChildren: function(lastProps, nextProps, transaction, context) {
    var lastContent =
      CONTENT_TYPES[typeof lastProps.children] ? lastProps.children : null;
    var nextContent =
      CONTENT_TYPES[typeof nextProps.children] ? nextProps.children : null;

    var lastHtml =
      lastProps.dangerouslySetInnerHTML &&
      lastProps.dangerouslySetInnerHTML.__html;
    var nextHtml =
      nextProps.dangerouslySetInnerHTML &&
      nextProps.dangerouslySetInnerHTML.__html;

    // Note the use of `!=` which checks for null or undefined.
    var lastChildren = lastContent != null ? null : lastProps.children;
    var nextChildren = nextContent != null ? null : nextProps.children;

    // If we're switching from children to content/html or vice versa, remove
    // the old content
    var lastHasContentOrHtml = lastContent != null || lastHtml != null;
    var nextHasContentOrHtml = nextContent != null || nextHtml != null;
    if (lastChildren != null && nextChildren == null) {
      this.updateChildren(null, transaction, context);
    } else if (lastHasContentOrHtml && !nextHasContentOrHtml) {
      this.updateTextContent('');
      if (__DEV__) {
        ReactInstrumentation.debugTool.onSetChildren(this._debugID, []);
      }
    }

    if (nextContent != null) {
      if (lastContent !== nextContent) {
        this.updateTextContent('' + nextContent);
        if (__DEV__) {
          setAndValidateContentChildDev.call(this, nextContent);
        }
      }
    } else if (nextHtml != null) {
      if (lastHtml !== nextHtml) {
        this.updateMarkup('' + nextHtml);
      }
      if (__DEV__) {
        ReactInstrumentation.debugTool.onSetChildren(this._debugID, []);
      }
    } else if (nextChildren != null) {
      if (__DEV__) {
        setAndValidateContentChildDev.call(this, null);
      }

      this.updateChildren(nextChildren, transaction, context);
    }
  },

  getHostNode: function() {
    return getNode(this);
  },

  /**
   * Destroys all event registrations for this instance. Does not remove from
   * the DOM. That must be done by the parent.
   *
   * @internal
   */
  unmountComponent: function(safely) {
    switch (this._tag) {
      case 'audio':
      case 'form':
      case 'iframe':
      case 'img':
      case 'link':
      case 'object':
      case 'source':
      case 'video':
        var listeners = this._wrapperState.listeners;
        if (listeners) {
          for (var i = 0; i < listeners.length; i++) {
            listeners[i].remove();
          }
        }
        break;
      case 'input':
      case 'textarea':
        inputValueTracking.stopTracking(this);
        break;
      case 'html':
      case 'head':
      case 'body':
        /**
         * Components like <html> <head> and <body> can't be removed or added
         * easily in a cross-browser way, however it's valuable to be able to
         * take advantage of React's reconciliation for styling and <title>
         * management. So we just document it and throw in dangerous cases.
         */
        invariant(
          false,
          '<%s> tried to unmount. Because of cross-browser quirks it is ' +
          'impossible to unmount some top-level components (eg <html>, ' +
          '<head>, and <body>) reliably and efficiently. To fix this, have a ' +
          'single top-level component that never unmounts render these ' +
          'elements.',
          this._tag
        );
        break;
    }

    this.unmountChildren(safely);
    ReactDOMComponentTree.uncacheNode(this);
    EventPluginHub.deleteAllListeners(this);
    this._rootNodeID = 0;
    this._domID = 0;
    this._wrapperState = null;

    if (__DEV__) {
      setAndValidateContentChildDev.call(this, null);
    }
  },

  getPublicInstance: function() {
    return getNode(this);
  },

};

Object.assign(
  ReactDOMComponent.prototype,
  ReactDOMComponent.Mixin,
  ReactMultiChild
);

module.exports = ReactDOMComponent;