Prototype1.5.1.1代码注释（三）

/*用的最多的怕就是这个方法了吧*/
function $(element) {
  if (arguments.length > 1) {
    for (var i = 0, elements = [], length = arguments.length; i < length; i++)
      elements.push($(arguments[i]));
    return elements;
  }
  if (typeof element == 'string')
    element = document.getElementById(element);
  return Element.extend(element);
}

/*定义getElementByClassName方法*/
if (Prototype.BrowserFeatures.XPath) {
  document._getElementsByXPath = function(expression, parentElement) {
    var results = [];
    var query = document.evaluate(expression, $(parentElement) || document,
      null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
    for (var i = 0, length = query.snapshotLength; i < length; i++)
      results.push(query.snapshotItem(i));
    return results;
  };

  document.getElementsByClassName = function(className, parentElement) {
    var q = ".//*[contains(concat(' ', @class, ' '), ' " + className + " ')]";
    return document._getElementsByXPath(q, parentElement);
  }

} else document.getElementsByClassName = function(className, parentElement) {
  var children = ($(parentElement) || document.body).getElementsByTagName('*');
  var elements = [], child, pattern = new RegExp("(^|\\s)" + className + "(\\s|$)");
  for (var i = 0, length = children.length; i < length; i++) {
    child = children[i];
    var elementClassName = child.className;
    if (elementClassName.length == 0) continue;
    if (elementClassName == className || elementClassName.match(pattern))
      elements.push(Element.extend(child));
  }
  return elements;
};

/*--------------------------------------------------------------------------*/

if (!window.Element) var Element = {};

Element.extend = function(element) {
  var F = Prototype.BrowserFeatures;
  /*
    element的nodeType属性：
        1 Element node. 
        3 Text node. 
  */
  /*
    只有在element
        1.包含tagName属性
        2.element不是text node
        3.element不包含_extended属性
        4.当前浏览器不是IE
        5.且element元素不是window对象
    的情况下才会继续执行
  */
  if (!element || !element.tagName || element.nodeType == 3 ||
   element._extended || F.SpecificElementExtensions || element == window)
    return element;

  var methods = {}, tagName = element.tagName, cache = Element.extend.cache,
   T = Element.Methods.ByTag;

  // extend methods for all tags ( Safari doesn't need this)
  /*从我测试的结果来看F.ElementExtensions在firefox上同样是true*/
  if (!F.ElementExtensions) {
    Object.extend(methods, Element.Methods),
    Object.extend(methods, Element.Methods.Simulated);
  }

  // extend methods for specific tags
  if (T[tagName]) Object.extend(methods, T[tagName]);

  for (var property in methods) {
    var value = methods[property];
    if (typeof value == 'function' && !(property in element))
      element[property] = cache.findOrStore(value);
  }
  /*这里定义了一把element._extended，飘逸啊。。。。完全一头雾水*/  
  element._extended = Prototype.emptyFunction;
  return element;
};

Element.extend.cache = {
  findOrStore: function(value) {
    return this[value] = this[value] || function() {
      return value.apply(null, [this].concat($A(arguments)));
    }
  }
};

/*定义了一些通用的methods
*/
Element.Methods = {
  visible: function(element) {
    return $(element).style.display != 'none';
  },

  toggle: function(element) {
    element = $(element);
    Element[Element.visible(element) ? 'hide' : 'show'](element);
    return element;
  },

  hide: function(element) {
    $(element).style.display = 'none';
    return element;
  },

  show: function(element) {
    $(element).style.display = '';
    return element;
  },

  remove: function(element) {
    element = $(element);
    element.parentNode.removeChild(element);
    return element;
  },

  update: function(element, html) {
    html = typeof html == 'undefined' ? '' : html.toString();
    $(element).innerHTML = html.stripScripts();
    /*这一步不太理解*/
    setTimeout(function() {html.evalScripts()}, 10);
    return element;
  },

  replace: function(element, html) {
    element = $(element);
    html = typeof html == 'undefined' ? '' : html.toString();
    /*IE里面定义了outerHTML而Firefox中没有这个属性*/
    if (element.outerHTML) {
      element.outerHTML = html.stripScripts();
    } else {
      /*取得包含element的document对象，并调用它的createRange方法*/
      /*Creates a TextRange object from the current text selection, or a controlRange collection from a control selection*/
      /*
      用Range进行选择，用selectNode()或者selectNodeContents()方法，这两个方法只有一个接收参数，一个DOM节点。
        selectNode()方法选择全部节点，包括它的孩子，而selectNodeContents()选择的节点只是它的孩子。如<p id="p1"><b>Hello</b> World</p>
        <script>
        var oRange1 = document.createRange();
        var oRange2 = document.createRange();
        var oP1 = document.getElementById("p1");
        oRange1.selectNode(oP1);
        oRange2.selectNodeContents(oP1);
        </script>
        使用selectNode方法，选择的部分如下：
        <p id="p1"><b>Hello</b> World</p>
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        而使用selectNodeContents方法，选择的部分如下：
        <p id="p1"><b>Hello</b> World</p>
                   ~~~~~~~~~~~~
      关于Range对象更多的说明，可以参考http://hi.baidu.com/llaa27/blog/item/2ea8f1f49fcb81daf2d385db.html
      */
      var range = element.ownerDocument.createRange();
      range.selectNodeContents(element);
      element.parentNode.replaceChild(
        range.createContextualFragment(html.stripScripts()), element);
    }
    setTimeout(function() {html.evalScripts()}, 10);
    return element;
  },

  inspect: function(element) {
    element = $(element);
    var result = '<' + element.tagName.toLowerCase();
    $H({'id': 'id', 'className': 'class'}).each(function(pair) {
      /*property对应DOM中对应的属性名
      attribute对应实际HTML文件中书写的代码
      举一个例子：
      <div id="content" class="div_content"></div>
      property       attribute
      ---------------------------
      "id"             "id"
      "className"     "class"
      ---------------------------
      */
      var property = pair.first(), attribute = pair.last();
      var value = (element[property] || '').toString();
      if (value) result += ' ' + attribute + '=' + value.inspect(true);
    });
    return result + '>';
  },
  /*
    <ul id="fruits">
      <li id="apples">
        <ul id="list-of-apples">
          <li id="golden-delicious"><p>Golden Delicious</p></li>
          <li id="mutsu">Mutsu</li>
          <li id="mcintosh">McIntosh</li>
          <li id="ida-red">Ida Red</li>
        </ul>
      </li>
    </ul>

    $('fruits').recursivelyCollect('firstChild');
    -> [li#apples, ul#list-of-apples, li#golden-delicious, p]
  */
  /*注：不包含text node*/
  recursivelyCollect: function(element, property) {
    element = $(element);
    var elements = [];
    while (element = element[property])
      if (element.nodeType == 1)
        elements.push(Element.extend(element));
    return elements;
  },

  /*收集某个元素的祖先列表*/
  /*注：不包含text node*/
  ancestors: function(element) {
    return $(element).recursivelyCollect('parentNode');
  },

  /*收集某个元素的子孙元素列表*/
  /*注：不包含text node*/
  descendants: function(element) {
    return $A($(element).getElementsByTagName('*')).each(Element.extend);
  },

  /*element的第一个子节点*/
  /*注：不包含text node*/
  firstDescendant: function(element) {
    element = $(element).firstChild;
    while (element && element.nodeType != 1) element = element.nextSibling;
    return $(element);
  },

  /*取得element所有子节点元素的列表*/
  /*
    <div id="australopithecus">
      <div id="homo-herectus">
        <div id="homo-neanderthalensis"></div>
        <div id="homo-sapiens"></div>
      </div>
    </div>

    $('australopithecus').immediateDescendants();
    -> [div#homo-herectus]

    $('homo-herectus').immediateDescendants();
    -> [div#homo-neanderthalensis, div#homo-sapiens]

    $('homo-sapiens').immediateDescendants();
    -> []
    */
    /*注：不包含text node*/
  immediateDescendants: function(element) {
    if (!(element = $(element).firstChild)) return [];
    while (element && element.nodeType != 1) element = element.nextSibling;
    if (element) return [element].concat($(element).nextSiblings());
    return [];
  },

  /*取得element所有的previous兄弟节点*/
  previousSiblings: function(element) {
    return $(element).recursivelyCollect('previousSibling');
  },

  /*取得element所有的next兄弟节点*/
  nextSiblings: function(element) {
    return $(element).recursivelyCollect('nextSibling');
  },

  /*element所有的兄弟节点*/
  siblings: function(element) {
    element = $(element);
    return element.previousSiblings().reverse().concat(element.nextSiblings());
  },

  match: function(element, selector) {
    if (typeof selector == 'string')
      selector = new Selector(selector);
    return selector.match($(element));
  },

  up: function(element, expression, index) {
    element = $(element);
    if (arguments.length == 1) return $(element.parentNode);
    var ancestors = element.ancestors();
    return expression ? Selector.findElement(ancestors, expression, index) :
      ancestors[index || 0];
  },

  down: function(element, expression, index) {
    element = $(element);
    if (arguments.length == 1) return element.firstDescendant();
    var descendants = element.descendants();
    return expression ? Selector.findElement(descendants, expression, index) :
      descendants[index || 0];
  },

  previous: function(element, expression, index) {
    element = $(element);
    if (arguments.length == 1) return $(Selector.handlers.previousElementSibling(element));
    var previousSiblings = element.previousSiblings();
    return expression ? Selector.findElement(previousSiblings, expression, index) :
      previousSiblings[index || 0];
  },

  next: function(element, expression, index) {
    element = $(element);
    if (arguments.length == 1) return $(Selector.handlers.nextElementSibling(element));
    var nextSiblings = element.nextSiblings();
    return expression ? Selector.findElement(nextSiblings, expression, index) :
      nextSiblings[index || 0];
  },

  getElementsBySelector: function() {
    var args = $A(arguments), element = $(args.shift());
    return Selector.findChildElements(element, args);
  },

  getElementsByClassName: function(element, className) {
    return document.getElementsByClassName(className, element);
  },

  
  /*可供查询的属性有：
  colspan,
  rowspan,
  valign,
  datetime,
  accesskey,
  tablindex,
  enctype,
  maxlength,
  readonly,
  longdesc,
  style,
  title,
  href,
  src,
  type,
  disabled,
  checked,
  readonly,
  multiple
  如果这里面没有的话可以直接调用Element._attributeTranslations.values["_getAttr"](ele,attr)
  也可以用Element._attributeTranslations.values["_flag"](ele,attr)来判断某个element是否包含指定属性
  */
  readAttribute: function(element, name) {
    element = $(element);
    if (Prototype.Browser.IE) {
      if (!element.attributes) return null;
      var t = Element._attributeTranslations;
      if (t.values[name]) return t.values[name](element, name);
      if (t.names[name])  name = t.names[name];
      var attribute = element.attributes[name];
      return attribute ? attribute.nodeValue : null;
    }
    return element.getAttribute(name);
  },

  getHeight: function(element) {
    return $(element).getDimensions().height;
  },

  getWidth: function(element) {
    return $(element).getDimensions().width;
  },

  classNames: function(element) {
    return new Element.ClassNames(element);
  },

  /*判断element是否有指定的className*/
  /*判断前element.className中前后的空格将会被忽略*/
  hasClassName: function(element, className) {
    if (!(element = $(element))) return;
    var elementClassName = element.className;
    if (elementClassName.length == 0) return false;
    if (elementClassName == className ||
        elementClassName.match(new RegExp("(^|\\s)" + className + "(\\s|$)")))
      return true;
    return false;
  },

  addClassName: function(element, className) {
    if (!(element = $(element))) return;
    Element.classNames(element).add(className);
    return element;
  },

  removeClassName: function(element, className) {
    if (!(element = $(element))) return;
    Element.classNames(element).remove(className);
    return element;
  },

  toggleClassName: function(element, className) {
    if (!(element = $(element))) return;
    Element.classNames(element)[element.hasClassName(className) ? 'remove' : 'add'](className);
    return element;
  },

  observe: function() {
    Event.observe.apply(Event, arguments);
    return $A(arguments).first();
  },

  stopObserving: function() {
    Event.stopObserving.apply(Event, arguments);
    return $A(arguments).first();
  },

  // removes whitespace-only text node children
  cleanWhitespace: function(element) {
    element = $(element);
    var node = element.firstChild;
    while (node) {
      var nextNode = node.nextSibling;
      if (node.nodeType == 3 && !/\S/.test(node.nodeValue))
        element.removeChild(node);
      node = nextNode;
    }
    return element;
  },

  /*判断element的innerHTML是否为空*/
  empty: function(element) {
    return $(element).innerHTML.blank();
  },

  /*判断element是否是ancestor的子孙节点*/
  descendantOf: function(element, ancestor) {
    element = $(element), ancestor = $(ancestor);
    while (element = element.parentNode)
      if (element == ancestor) return true;
    return false;
  },

  /*网页卷动到指定元素的位置*/
  scrollTo: function(element) {
    element = $(element);
    var pos = Position.cumulativeOffset(element);
    window.scrollTo(pos[0], pos[1]);
    return element;
  },
 
  
  getStyle: function(element, style) {
    element = $(element);
    style = style == 'float' ? 'cssFloat' : style.camelize();
    var value = element.style[style];
    if (!value) {
      var css = document.defaultView.getComputedStyle(element, null);
      value = css ? css[style] : null;
    }
    if (style == 'opacity') return value ? parseFloat(value) : 1.0;
    return value == 'auto' ? null : value;
  },

  getOpacity: function(element) {
    return $(element).getStyle('opacity');
  },

  setStyle: function(element, styles, camelized) {
    element = $(element);
    var elementStyle = element.style;

    for (var property in styles)
      if (property == 'opacity') element.setOpacity(styles[property])
      else
        elementStyle[(property == 'float' || property == 'cssFloat') ?
          (elementStyle.styleFloat === undefined ? 'cssFloat' : 'styleFloat') :
          (camelized ? property : property.camelize())] = styles[property];

    return element;
  },

  /*设置透明度*/
  setOpacity: function(element, value) {
    element = $(element);
    element.style.opacity = (value == 1 || value === '') ? '' :
      (value < 0.00001) ? 0 : value;
    return element;
  },

  /*取得DOM元素的大小*/
  getDimensions: function(element) {
    element = $(element);
    var display = $(element).getStyle('display');
    if (display != 'none' && display != null) // Safari bug
      return {width: element.offsetWidth, height: element.offsetHeight};

    // All *Width and *Height properties give 0 on elements with display none,
    // so enable the element temporarily
    var els = element.style;
    var originalVisibility = els.visibility;
    var originalPosition = els.position;
    var originalDisplay = els.display;
    els.visibility = 'hidden';
    els.position = 'absolute';
    els.display = 'block';
    var originalWidth = element.clientWidth;
    var originalHeight = element.clientHeight;
    els.display = originalDisplay;
    els.position = originalPosition;
    els.visibility = originalVisibility;
    return {width: originalWidth, height: originalHeight};
  },

  /*把一个元素的postion从static改为relative*/
  makePositioned: function(element) {
    element = $(element);
    var pos = Element.getStyle(element, 'position');
    if (pos == 'static' || !pos) {
      //这里留下一个记号，表示此元素曾经使用过makePositioned方法
      element._madePositioned = true;
      element.style.position = 'relative';
      // Opera returns the offset relative to the positioning context, when an
      // element is position relative but top and left have not been defined
      if (window.opera) {
        element.style.top = 0;
        element.style.left = 0;
      }
    }
    return element;
  },

  undoPositioned: function(element) {
    element = $(element);
    //必须先makePositioned之后才能undoPositioned
    if (element._madePositioned) {
      //销毁makePositioned的证据
      element._madePositioned = undefined;
      element.style.position =
        element.style.top =
        element.style.left =
        element.style.bottom =
        element.style.right = '';
    }
    return element;
  },

  //设置某个元素的overflow属性为hidden，也就是说超出的地方会被隐藏
  makeClipping: function(element) {
    element = $(element);
    if (element._overflow) return element;
    element._overflow = element.style.overflow || 'auto';
    if ((Element.getStyle(element, 'overflow') || 'visible') != 'hidden')
      element.style.overflow = 'hidden';
    return element;
  },

  //如果对某个元素调用过makeClipping，调用undoClipping会设置overflow属性回auto
  undoClipping: function(element) {
    element = $(element);
    if (!element._overflow) return element;
    element.style.overflow = element._overflow == 'auto' ? '' : element._overflow;
    element._overflow = null;
    return element;
  }
};

Object.extend(Element.Methods, {
  childOf: Element.Methods.descendantOf,
  childElements: Element.Methods.immediateDescendants
});

if (Prototype.Browser.Opera) {
  Element.Methods._getStyle = Element.Methods.getStyle;
  Element.Methods.getStyle = function(element, style) {
    switch(style) {
      case 'left':
      case 'top':
      case 'right':
      case 'bottom':
        if (Element._getStyle(element, 'position') == 'static') return null;
      default: return Element._getStyle(element, style);
    }
  };
}
else if (Prototype.Browser.IE) {
  Element.Methods.getStyle = function(element, style) {
    element = $(element);
    style = (style == 'float' || style == 'cssFloat') ? 'styleFloat' : style.camelize();
    var value = element.style[style];
    if (!value && element.currentStyle) value = element.currentStyle[style];

    if (style == 'opacity') {
      if (value = (element.getStyle('filter') || '').match(/alpha\(opacity=(.*)\)/))
        if (value[1]) return parseFloat(value[1]) / 100;
      return 1.0;
    }

    if (value == 'auto') {
      if ((style == 'width' || style == 'height') && (element.getStyle('display') != 'none'))
        return element['offset'+style.capitalize()] + 'px';
      return null;
    }
    return value;
  };

  Element.Methods.setOpacity = function(element, value) {
    element = $(element);
    var filter = element.getStyle('filter'), style = element.style;
    if (value == 1 || value === '') {
      style.filter = filter.replace(/alpha\([^\)]*\)/gi,'');
      return element;
    } else if (value < 0.00001) value = 0;
    style.filter = filter.replace(/alpha\([^\)]*\)/gi, '') +
      'alpha(opacity=' + (value * 100) + ')';
    return element;
  };

  // IE is missing .innerHTML support for TABLE-related elements
  // 因为IE在处理THEAD,TBODY,TR,TD的时候没有.innerHTML属性，所以只能采用appendChild的方式来曲线救国
  // 首先创建一个包含Table元素的DIV,将要替换的html添加到div的table中，这样就可以利用table以node的方法
  // 读取要添加的html元素，再把这些node添加到element中去
  Element.Methods.update = function(element, html) {
    element = $(element);
    html = typeof html == 'undefined' ? '' : html.toString();
    var tagName = element.tagName.toUpperCase();
    if (['THEAD','TBODY','TR','TD'].include(tagName)) {
      var div = document.createElement('div');
      switch (tagName) {
        case 'THEAD':
        case 'TBODY':
          div.innerHTML = '<table><tbody>' +  html.stripScripts() + '</tbody></table>';
          depth = 2;
          break;
        case 'TR':
          div.innerHTML = '<table><tbody><tr>' +  html.stripScripts() + '</tr></tbody></table>';
          depth = 3;
          break;
        case 'TD':
          div.innerHTML = '<table><tbody><tr><td>' +  html.stripScripts() + '</td></tr></tbody></table>';
          depth = 4;
      }
      $A(element.childNodes).each(function(node) { element.removeChild(node) });
      depth.times(function() { div = div.firstChild });
      $A(div.childNodes).each(function(node) { element.appendChild(node) });
    } else {
      element.innerHTML = html.stripScripts();
    }
    setTimeout(function() { html.evalScripts() }, 10);
    return element;
  }
}
else if (Prototype.Browser.Gecko) {
  Element.Methods.setOpacity = function(element, value) {
    element = $(element);
    element.style.opacity = (value == 1) ? 0.999999 :
      (value === '') ? '' : (value < 0.00001) ? 0 : value;
    return element;
  };
}

/*关于getAttribute说明
    Retrieves the value of the specified attribute. 

    Syntax

    vAttrValue = object.getAttribute(sAttrName [, iFlags])
    Parameters

    sAttrName Required. String that specifies the name of the attribute. 
    iFlags Optional. Integer that specifies one or more of the following flags:
    0 Default. Performs a property search that is not case-sensitive, and returns an interpolated value if the property is found. 
    1 Performs a case-sensitive property search. To find a match, the uppercase and lowercase letters in sAttrName must exactly match those in the attribute name. If the iFlags parameter for getAttribute is set to 1 and this option is set to 0 (default), the specified property name might not be found. 
    2 Returns the value exactly as it was set in script or in the source document. 
     

    Return Value
    Variant that returns a String, number, or Boolean value as defined by the attribute. If the attribute is not present, this method returns null. 
*/
Element._attributeTranslations = {
  names: {
    colspan:   "colSpan",
    rowspan:   "rowSpan",
    valign:    "vAlign",
    datetime:  "dateTime",
    accesskey: "accessKey",
    tabindex:  "tabIndex",
    enctype:   "encType",
    maxlength: "maxLength",
    readonly:  "readOnly",
    longdesc:  "longDesc"
  },
  values: {
    //取得attribute node
    _getAttr: function(element, attribute) {
      return element.getAttribute(attribute, 2);
    },
    //判断是否包含某个attribute
    _flag: function(element, attribute) {
      return $(element).hasAttribute(attribute) ? attribute : null;
    },
    //获得DOM中style属性的内容
    style: function(element) {
      return element.style.cssText.toLowerCase();
    },
    //获得DOM元素title属性的内用
    title: function(element) {
      var node = element.getAttributeNode('title');
      return node.specified ? node.nodeValue : null;
    }
  }
};

/*给Element._attributeTranslations.values添加了7个方法
之所以写在外面完全是为了DRY吧
href,
src,
type,
disabled,
checked,
readonly,
multiple
这样话基本上所有的属性都覆盖到了，除了一些不常用的，例如dir,lang等
*/
(function() {
  Object.extend(this, {
    href: this._getAttr,
    src:  this._getAttr,
    type: this._getAttr,
    disabled: this._flag,
    checked:  this._flag,
    readonly: this._flag,
    multiple: this._flag
  });
}).call(Element._attributeTranslations.values);

/* getAttributeNode方法说明
    Retrieves an attribute object referenced by the attribute.name property.

    Syntax

    oAttribute = object.getAttributeNode(sName)
    Parameters

    sName Required. String that specifies the name property of the requested attribute object. 

    Return Value

    Returns a reference to an attribute object.
*/
Element.Methods.Simulated = {
  hasAttribute: function(element, attribute) {
    var t = Element._attributeTranslations, node;
    attribute = t.names[attribute] || attribute;
    node = $(element).getAttributeNode(attribute);
    return node && node.specified;
  }
};

Element.Methods.ByTag = {};

Object.extend(Element, Element.Methods);

if (!Prototype.BrowserFeatures.ElementExtensions &&
 document.createElement('div').__proto__) {
  window.HTMLElement = {};
  window.HTMLElement.prototype = document.createElement('div').__proto__;
  Prototype.BrowserFeatures.ElementExtensions = true;
}

Element.hasAttribute = function(element, attribute) {
  if (element.hasAttribute) return element.hasAttribute(attribute);
  return Element.Methods.Simulated.hasAttribute(element, attribute);
};

Element.addMethods = function(methods) {
  var F = Prototype.BrowserFeatures, T = Element.Methods.ByTag;

  if (!methods) {
    Object.extend(Form, Form.Methods);
    Object.extend(Form.Element, Form.Element.Methods);
    Object.extend(Element.Methods.ByTag, {
    //在Element.Methods.ByTag下产生四个命名空间，各自下面有不同标签对应的方法
      "FORM":     Object.clone(Form.Methods),
      "INPUT":    Object.clone(Form.Element.Methods),
      "SELECT":   Object.clone(Form.Element.Methods),
      "TEXTAREA": Object.clone(Form.Element.Methods)
    });
  }

  if (arguments.length == 2) {
    var tagName = methods;
    methods = arguments[1];
  }

  if (!tagName) Object.extend(Element.Methods, methods || {});
  else {
    if (tagName.constructor == Array) tagName.each(extend);
    else extend(tagName);
  }

  function extend(tagName) {
    tagName = tagName.toUpperCase();
    if (!Element.Methods.ByTag[tagName])
      Element.Methods.ByTag[tagName] = {};
    Object.extend(Element.Methods.ByTag[tagName], methods);
  }

  function copy(methods, destination, onlyIfAbsent) {
    onlyIfAbsent = onlyIfAbsent || false;
    var cache = Element.extend.cache;
    for (var property in methods) {
      var value = methods[property];
      if (!onlyIfAbsent || !(property in destination))
        destination[property] = cache.findOrStore(value);
    }
  }

  function findDOMClass(tagName) {
    var klass;
    var trans = {
      "OPTGROUP": "OptGroup", "TEXTAREA": "TextArea", "P": "Paragraph",
      "FIELDSET": "FieldSet", "UL": "UList", "OL": "OList", "DL": "DList",
      "DIR": "Directory", "H1": "Heading", "H2": "Heading", "H3": "Heading",
      "H4": "Heading", "H5": "Heading", "H6": "Heading", "Q": "Quote",
      "INS": "Mod", "DEL": "Mod", "A": "Anchor", "IMG": "Image", "CAPTION":
      "TableCaption", "COL": "TableCol", "COLGROUP": "TableCol", "THEAD":
      "TableSection", "TFOOT": "TableSection", "TBODY": "TableSection", "TR":
      "TableRow", "TH": "TableCell", "TD": "TableCell", "FRAMESET":
      "FrameSet", "IFRAME": "IFrame"
    };
    if (trans[tagName]) klass = 'HTML' + trans[tagName] + 'Element';
    if (window[klass]) return window[klass];
    klass = 'HTML' + tagName + 'Element';
    if (window[klass]) return window[klass];
    klass = 'HTML' + tagName.capitalize() + 'Element';
    if (window[klass]) return window[klass];

    window[klass] = {};
    window[klass].prototype = document.createElement(tagName).__proto__;
    return window[klass];
  }

  if (F.ElementExtensions) {
    copy(Element.Methods, HTMLElement.prototype);
    copy(Element.Methods.Simulated, HTMLElement.prototype, true);
  }

  if (F.SpecificElementExtensions) {
    for (var tag in Element.Methods.ByTag) {
      var klass = findDOMClass(tag);
      if (typeof klass == "undefined") continue;
      copy(T[tag], klass.prototype);
    }
  }

  Object.extend(Element, Element.Methods);
  delete Element.ByTag;
};

var Toggle = { display: Element.toggle };

/*--------------------------------------------------------------------------*/

Abstract.Insertion = function(adjacency) {
  this.adjacency = adjacency;
}

/*
    Inserts the given HTML text into the element at the location.

    Syntax

    object.insertAdjacentHTML(sWhere, sText)
    Parameters

    sWhere Required. String that specifies where to insert the HTML text, using one of the following values: beforeBegin Inserts sText immediately before the object. 
    afterBegin Inserts sText after the start of the object but before all other content in the object. 
    beforeEnd Inserts sText immediately before the end of the object but after all other content in the object. 
    afterEnd Inserts sText immediately after the end of the object. 
     
    sText Required. String that specifies the HTML text to insert. The string can be a combination of text and HTML tags. This must be well-formed, valid HTML or this method will fail. 
*/
Abstract.Insertion.prototype = {
  initialize: function(element, content) {
    this.element = $(element);
    this.content = content.stripScripts();

    if (this.adjacency && this.element.insertAdjacentHTML) {
      try {
        this.element.insertAdjacentHTML(this.adjacency, this.content);
      } catch (e) {
        var tagName = this.element.tagName.toUpperCase();
        // 在TBODY和TR前插入对象与众不同
        if (['TBODY', 'TR'].include(tagName)) {
          this.insertContent(this.contentFromAnonymousTable());
        } else {
          throw e;
        }
      }
    } else {
      this.range = this.element.ownerDocument.createRange();
      if (this.initializeRange) this.initializeRange();
      this.insertContent([this.range.createContextualFragment(this.content)]);
    }

    setTimeout(function() {content.evalScripts()}, 10);
  },

  // 构造一个匿名table，然后把指定的内容插到<tbody></tbody>之间
  // 最后返回一个代表指定内容的node对象
  contentFromAnonymousTable: function() {
    var div = document.createElement('div');
    div.innerHTML = '<table><tbody>' + this.content + '</tbody></table>';
    return $A(div.childNodes[0].childNodes[0].childNodes);
  }
}

var Insertion = new Object();

Insertion.Before = Class.create();
Insertion.Before.prototype = Object.extend(new Abstract.Insertion('beforeBegin'), {
  initializeRange: function() {
    this.range.setStartBefore(this.element);
  },

  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.parentNode.insertBefore(fragment, this.element);
    }).bind(this));
  }
});

Insertion.Top = Class.create();
Insertion.Top.prototype = Object.extend(new Abstract.Insertion('afterBegin'), {
  initializeRange: function() {
    this.range.selectNodeContents(this.element);
    this.range.collapse(true);
  },

  insertContent: function(fragments) {
    fragments.reverse(false).each((function(fragment) {
      this.element.insertBefore(fragment, this.element.firstChild);
    }).bind(this));
  }
});

Insertion.Bottom = Class.create();
Insertion.Bottom.prototype = Object.extend(new Abstract.Insertion('beforeEnd'), {
  initializeRange: function() {
    this.range.selectNodeContents(this.element);
    this.range.collapse(this.element);
  },

  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.appendChild(fragment);
    }).bind(this));
  }
});

Insertion.After = Class.create();
Insertion.After.prototype = Object.extend(new Abstract.Insertion('afterEnd'), {
  initializeRange: function() {
    this.range.setStartAfter(this.element);
  },

  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.parentNode.insertBefore(fragment,
        this.element.nextSibling);
    }).bind(this));
  }
});

/*--------------------------------------------------------------------------*/

Element.ClassNames = Class.create();
Element.ClassNames.prototype = {
  initialize: function(element) {
    this.element = $(element);
  },

  _each: function(iterator) {
    this.element.className.split(/\s+/).select(function(name) {
      return name.length > 0;
    })._each(iterator);
  },

  set: function(className) {
    this.element.className = className;
  },

  add: function(classNameToAdd) {
    if (this.include(classNameToAdd)) return;
    this.set($A(this).concat(classNameToAdd).join(' '));
  },

  remove: function(classNameToRemove) {
    if (!this.include(classNameToRemove)) return;
    this.set($A(this).without(classNameToRemove).join(' '));
  },

  toString: function() {
    return $A(this).join(' ');
  }
};