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    snowolf

    這樣的一種生活
    posts - 23, comments - 5, trackbacks - 0, articles - 11

    prototype.js 1.4 原代碼閱讀

    Posted on 2007-05-11 23:05 snowolf 閱讀(345) 評論(0)  編輯  收藏

    /**
     * 定義一個全局對象, 屬性 Version 在發布的時候會替換為當前版本號
     */
    var Prototype = {
      Version: '1.5.0_rc0',
      ScriptFragment: '(?:<script.*?>)((\n|\r|.)*?)(?:<\/script>)',

      emptyFunction: function() {},
      K: function(x) {return x}
    }

    /**
     * 創建一種類型,注意其屬性 create 是一個方法,返回一個構造函數。
     * 一般使用如下 
     *     var X = Class.create();  返回一個類型,類似于 java 的一個Class實例。
     * 要使用 X 類型,需繼續用 new X()來獲取一個實例,如同 java 的 Class.newInstance()方法。
     *
     * 返回的構造函數會執行名為 initialize 的方法, initialize 是 Ruby 對象的構造器方法名字。
     * 此時initialize方法還沒有定義,其后的代碼中創建新類型時會建立相應的同名方法。
     *
     * 如果一定要從java上去理解。你可以理解為用Class.create()創建一個繼承java.lang.Class類的類。當然java不允許這樣做,因為Class類是final的
     *
     */
    var Class = {
      create: function() {
        return function() {
          this.initialize.apply(this, arguments);
        }
      }
    }

    /**
     * 創建一個對象,從變量名來思考,本意也許是定義一個抽象類,以后創建新對象都 extend 它。
     * 但從其后代碼的應用來看, Abstract 更多是為了保持命名空間清晰的考慮。
     * 也就是說,我們可以給 Abstract 這個對象實例添加新的對象定義。
     *
     * 從java去理解,就是動態給一個對象創建內部類。
     */
    var Abstract = new Object();

    /**
     * 獲取參數對象的所有屬性和方法,有點象多重繼承。但是這種繼承是動態獲得的。
     * 如:
     *     var a = new ObjectA(), b = new ObjectB();
     *     var c = a.extend(b);
     * 此時 c 對象同時擁有 a 和 b 對象的屬性和方法。但是與多重繼承不同的是,c instanceof ObjectB 將返回false。
     */
    Object.extend = function(destination, source) {
      for (var property in source) {
        destination[property] = source[property];
      }
      return destination;
    }

    Object.inspect = function(object) {
      try {
        if (object == undefined) return 'undefined';
        if (object == null) return 'null';
        return object.inspect ? object.inspect() : object.toString();
      } catch (e) {
        if (e instanceof RangeError) return '...';
        throw e;
      }
    }

    /**
     * 這個方法很有趣,它封裝一個javascript函數對象,返回一個新函數對象,新函數對象的主體和原對象相同,但是bind()方法參數將被用作當前對象的對象。
     * 也就是說新函數中的 this 引用被改變為參數提供的對象。
     * 比如:
     *     <input type="text" id="aaa" value="aaa">
     *     <input type="text" id="bbb" value="bbb">
     *     .................
     *     <script>
     *         var aaa = document.getElementById("aaa");
     *         var bbb = document.getElementById("bbb"); *         aaa.showValue = function() {alert(this.value);}
     *         aaa.showValue2 = aaa.showValue.bind(bbb);
     *     </script>
     *  那么,調用aaa.showValue 將返回"aaa", 但調用aaa.showValue2 將返回"bbb"。
     *
     * apply 是ie5.5后才出現的新方法(Netscape好像很早就支持了)。
     * 該方法更多的資料參考MSDN http://msdn.microsoft.com/library/en-us/script56/html/js56jsmthApply.asp
     * 還有一個 call 方法,應用起來和 apply 類似。可以一起研究下。
     */
    Function.prototype.bind = function() {
      var __method = this, args = $A(arguments), object = args.shift();
      return function() {
        return __method.apply(object, args.concat($A(arguments)));
      }
    }

    /**
     * 和bind一樣,不過這個方法一般用做html控件對象的事件處理。所以要傳遞event對象
     * 注意這時候,用到了 Function.call。它與 Function.apply 的不同好像僅僅是對參數形式的定義。
     * 如同 java 兩個過載的方法。
     */
    Function.prototype.bindAsEventListener = function(object) {
      var __method = this;
      return function(event) {
        return __method.call(object, event || window.event);
      }
    }

    /**
     * 將整數形式RGB顏色值轉換為HEX形式
     */
    Object.extend(Number.prototype, {
      toColorPart: function() {
        var digits = this.toString(16);
        if (this < 16) return '0' + digits;
        return digits;
      },

      succ: function() {
        return this + 1;
      },

      times: function(iterator) {
        $R(0, this, true).each(iterator);
        return this;
      }
    });

    /**
     * 典型 Ruby 風格的函數,將參數中的方法逐個調用,返回第一個成功執行的方法的返回值
     */
    var Try = {
      these: function() {
        var returnValue;

        for (var i = 0; i < arguments.length; i++) {
          var lambda = arguments[i];
          try {
            returnValue = lambda();
            break;
          } catch (e) {}
        }

        return returnValue;
      }
    }

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

    /**
     * 一個設計精巧的定時執行器
     * 首先由 Class.create() 創建一個 PeriodicalExecuter 類型,
     * 然后用對象直接量的語法形式設置原型。
     *
     * 需要特別說明的是 rgisterCallback 方法,它調用上面定義的函數原型方法bind, 并傳遞自己為參數。
     * 之所以這樣做,是因為 setTimeout 默認總以 window 對象為當前對象,也就是說,如果 registerCallback 方法定義如下的話:
     *     registerCallback: function() {
     *         setTimeout(this.onTimerEvent, this.frequency * 1000);
     *     }
     * 那么,this.onTimeoutEvent 方法執行失敗,因為它無法訪問 this.currentlyExecuting 屬性。* 而使用了bind以后,該方法才能正確的找到this,也就是PeriodicalExecuter的當前實例。
     */
    var PeriodicalExecuter = Class.create();
    PeriodicalExecuter.prototype = {
      initialize: function(callback, frequency) {
        this.callback = callback;
        this.frequency = frequency;
        this.currentlyExecuting = false;

        this.registerCallback();
      },

      registerCallback: function() {
        setInterval(this.onTimerEvent.bind(this), this.frequency * 1000);
      },

      onTimerEvent: function() {
        if (!this.currentlyExecuting) {
          try {
            this.currentlyExecuting = true;
            this.callback();
          } finally {
            this.currentlyExecuting = false;
          }
        }
      }
    }
    Object.extend(String.prototype, {
      gsub: function(pattern, replacement) {
        var result = '', source = this, match;
        replacement = arguments.callee.prepareReplacement(replacement);

        while (source.length > 0) {
          if (match = source.match(pattern)) {
            result += source.slice(0, match.index);
            result += (replacement(match) || '').toString();
            source  = source.slice(match.index + match[0].length);
          } else {
            result += source, source = '';
          }
        }
        return result;
      },

      sub: function(pattern, replacement, count) {
        replacement = this.gsub.prepareReplacement(replacement);
        count = count === undefined ? 1 : count;

        return this.gsub(pattern, function(match) {
          if (--count < 0) return match[0];
          return replacement(match);
        });
      },

      scan: function(pattern, iterator) {
        this.gsub(pattern, iterator);
        return this;
      },

      truncate: function(length, truncation) {
        length = length || 30;
        truncation = truncation === undefined ? '...' : truncation;
        return this.length > length ?
          this.slice(0, length - truncation.length) + truncation : this;
      },

      strip: function() {
        return this.replace(/^\s+/, '').replace(/\s+$/, '');
      },

      stripTags: function() {
        return this.replace(/<\/?[^>]+>/gi, '');
      },

      stripScripts: function() {
        return this.replace(new RegExp(Prototype.ScriptFragment, 'img'), '');
      },extractScripts: function() {
        var matchAll = new RegExp(Prototype.ScriptFragment, 'img');
        var matchOne = new RegExp(Prototype.ScriptFragment, 'im');
        return (this.match(matchAll) || []).map(function(scriptTag) {
          return (scriptTag.match(matchOne) || ['', ''])[1];
        });
      },

      evalScripts: function() {
        return this.extractScripts().map(function(script) { return eval(script) });
      },

      escapeHTML: function() {
        var div = document.createElement('div');
        var text = document.createTextNode(this);
        div.appendChild(text);
        return div.innerHTML;
      },

      unescapeHTML: function() {
        var div = document.createElement('div');
        div.innerHTML = this.stripTags();
        return div.childNodes[0] ? div.childNodes[0].nodeValue : '';
      },

      toQueryParams: function() {
        var pairs = this.match(/^\??(.*)$/)[1].split('&');
        return pairs.inject({}, function(params, pairString) {
          var pair = pairString.split('=');
          params[pair[0]] = pair[1];
          return params;
        });
      },

      toArray: function() {
        return this.split('');
      },

      camelize: function() {
        var oStringList = this.split('-');
        if (oStringList.length == 1) return oStringList[0];

        var camelizedString = this.indexOf('-') == 0
          ? oStringList[0].charAt(0).toUpperCase() + oStringList[0].substring(1)
          : oStringList[0];

        for (var i = 1, len = oStringList.length; i < len; i++) {
          var s = oStringList[i];
          camelizedString += s.charAt(0).toUpperCase() + s.substring(1);
        }

        return camelizedString;
      },

      inspect: function() {
        return "'" + this.replace(/\\/g, '\\\\').replace(/'/g, '\\\'') + "'";
      }
    });

    String.prototype.gsub.prepareReplacement = function(replacement) {
      if (typeof replacement == 'function') return replacement;
      var template = new Template(replacement);
      return function(match) { return template.evaluate(match) };
    }

    String.prototype.parseQuery = String.prototype.toQueryParams;

    var Template = Class.create();
    Template.Pattern = /(^|.|\r|\n)(#\{(.*?)\})/;
    Template.prototype = {
      initialize: function(template, pattern) {
        this.template = template.toString();
        this.pattern  = pattern || Template.Pattern;
      },

      evaluate: function(object) {
        return this.template.gsub(this.pattern, function(match) {
          var before = match[1]; if (before == '\\') return match[2];
          return before + (object[match[3]] || '').toString();
        });
      }
    }

    var $break    = new Object();
    var $continue = new Object();

    var Enumerable = {
      each: function(iterator) {
        var index = 0;
        try {
          this._each(function(value) {
            try {
              iterator(value, index++);
            } catch (e) {
              if (e != $continue) throw e;
            }
          });
        } catch (e) {
          if (e != $break) throw e;
        }
      },

      all: function(iterator) {
        var result = true;
        this.each(function(value, index) {
          result = result && !!(iterator || Prototype.K)(value, index);
          if (!result) throw $break;
        });
        return result;
      },

      any: function(iterator) {
        var result = true;
        this.each(function(value, index) {
          if (result = !!(iterator || Prototype.K)(value, index))
            throw $break;
        });
        return result;
      },

      collect: function(iterator) {
        var results = [];
        this.each(function(value, index) {
          results.push(iterator(value, index));
        });
        return results;
      },

      detect: function (iterator) {
        var result;
        this.each(function(value, index) {
          if (iterator(value, index)) {
            result = value;
            throw $break;
          }
        });
        return result;
      },

      findAll: function(iterator) {
        var results = [];
        this.each(function(value, index) {
          if (iterator(value, index))
            results.push(value);
        });
        return results;
      },

      grep: function(pattern, iterator) {
        var results = [];
        this.each(function(value, index) {
          var stringValue = value.toString();
          if (stringValue.match(pattern))
            results.push((iterator || Prototype.K)(value, index));
        })
        return results;
      },

      include: function(object) {
        var found = false; this.each(function(value) {
          if (value == object) {
            found = true;
            throw $break;
          }
        });
        return found;
      },

      inject: function(memo, iterator) {
        this.each(function(value, index) {
          memo = iterator(memo, value, index);
        });
        return memo;
      },

      invoke: function(method) {
        var args = $A(arguments).slice(1);
        return this.collect(function(value) {
          return value[method].apply(value, args);
        });
      },

      max: function(iterator) {
        var result;
        this.each(function(value, index) {
          value = (iterator || Prototype.K)(value, index);
          if (result == undefined || value >= result)
            result = value;
        });
        return result;
      },

      min: function(iterator) {
        var result;
        this.each(function(value, index) {
          value = (iterator || Prototype.K)(value, index);
          if (result == undefined || value < result)
            result = value;
        });
        return result;
      },

      partition: function(iterator) {
        var trues = [], falses = [];
        this.each(function(value, index) {
          ((iterator || Prototype.K)(value, index) ?
            trues : falses).push(value);
        });
        return [trues, falses];
      },

      pluck: function(property) {
        var results = [];
        this.each(function(value, index) {
          results.push(value[property]);
        });
        return results;
      },

      reject: function(iterator) {
        var results = [];
        this.each(function(value, index) {
          if (!iterator(value, index))
            results.push(value);
        });
        return results;
      },

      sortBy: function(iterator) {
        return this.collect(function(value, index) {
          return {value: value, criteria: iterator(value, index)};
        }).sort(function(left, right) {
          var a = left.criteria, b = right.criteria;
          return a < b ? -1 : a > b ? 1 : 0;
        }).pluck('value');
      },

      toArray: function() {
        return this.collect(Prototype.K);
      }, zip: function() {
        var iterator = Prototype.K, args = $A(arguments);
        if (typeof args.last() == 'function')
          iterator = args.pop();

        var collections = [this].concat(args).map($A);
        return this.map(function(value, index) {
          return iterator(collections.pluck(index));
        });
      },

      inspect: function() {
        return '#<Enumerable:' + this.toArray().inspect() + '>';
      }
    }

    Object.extend(Enumerable, {
      map:     Enumerable.collect,
      find:    Enumerable.detect,
      select:  Enumerable.findAll,
      member:  Enumerable.include,
      entries: Enumerable.toArray
    });
    var $A = Array.from = function(iterable) {
      if (!iterable) return [];
      if (iterable.toArray) {
        return iterable.toArray();
      } else {
        var results = [];
        for (var i = 0; i < iterable.length; i++)
          results.push(iterable[i]);
        return results;
      }
    }

    Object.extend(Array.prototype, Enumerable);

    if (!Array.prototype._reverse)
      Array.prototype._reverse = Array.prototype.reverse;

    Object.extend(Array.prototype, {
      _each: function(iterator) {
        for (var i = 0; i < this.length; i++)
          iterator(this[i]);
      },

      clear: function() {
        this.length = 0;
        return this;
      },

      first: function() {
        return this[0];
      },

      last: function() {
        return this[this.length - 1];
      },

      compact: function() {
        return this.select(function(value) {
          return value != undefined || value != null;
        });
      },

      flatten: function() {
        return this.inject([], function(array, value) {
          return array.concat(value && value.constructor == Array ?
            value.flatten() : [value]);
        });
      },

      without: function() {
        var values = $A(arguments);
        return this.select(function(value) {
          return !values.include(value);
        });
      },

      indexOf: function(object) {
        for (var i = 0; i < this.length; i++)
          if (this[i] == object) return i;
        return -1;
      },

      reverse: function(inline) {
        return (inline !== false ? this : this.toArray())._reverse();
      },

      inspect: function() {
        return '[' + this.map(Object.inspect).join(', ') + ']';
      }
    });
    var Hash = {
      _each: function(iterator) {
        for (var key in this) {
          var value = this[key];if (typeof value == 'function') continue;

          var pair = [key, value];
          pair.key = key;
          pair.value = value;
          iterator(pair);
        }
      },

      keys: function() {
        return this.pluck('key');
      },

      values: function() {
        return this.pluck('value');
      },

      merge: function(hash) {
        return $H(hash).inject($H(this), function(mergedHash, pair) {
          mergedHash[pair.key] = pair.value;
          return mergedHash;
        });
      },

      toQueryString: function() {
        return this.map(function(pair) {
          return pair.map(encodeURIComponent).join('=');
        }).join('&');
      },

      inspect: function() {
        return '#<Hash:{' + this.map(function(pair) {
          return pair.map(Object.inspect).join(': ');
        }).join(', ') + '}>';
      }
    }

    function $H(object) {
      var hash = Object.extend({}, object || {});
      Object.extend(hash, Enumerable);
      Object.extend(hash, Hash);
      return hash;
    }
    ObjectRange = Class.create();
    Object.extend(ObjectRange.prototype, Enumerable);
    Object.extend(ObjectRange.prototype, {
      initialize: function(start, end, exclusive) {
        this.start = start;
        this.end = end;
        this.exclusive = exclusive;
      },

      _each: function(iterator) {
        var value = this.start;
        do {
          iterator(value);
          value = value.succ();
        } while (this.include(value));
      },

      include: function(value) {
        if (value < this.start)
          return false;
        if (this.exclusive)
          return value < this.end;
        return value <= this.end;
      }
    });

    var $R = function(start, end, exclusive) {
      return new ObjectRange(start, end, exclusive);
    }

    /**
     * 定義 Ajax 對象, 靜態方法 getTransport 方法返回一個 XMLHttp 對象
     */
    var Ajax = {
      getTransport: function() {
        return Try.these(
          function() {return new XMLHttpRequest()},
          function() {return new ActiveXObject('Msxml2.XMLHTTP')},
          function() {return new ActiveXObject('Microsoft.XMLHTTP')}
        ) || false;
      },

      activeRequestCount: 0
    }

    Ajax.Responders = {
      responders: [],

      _each: function(iterator) {
        this.responders._each(iterator);
      },

      register: function(responderToAdd) {
        if (!this.include(responderToAdd))
          this.responders.push(responderToAdd);},

      unregister: function(responderToRemove) {
        this.responders = this.responders.without(responderToRemove);
      },

      dispatch: function(callback, request, transport, json) {
        this.each(function(responder) {
          if (responder[callback] && typeof responder[callback] == 'function') {
            try {
              responder[callback].apply(responder, [request, transport, json]);
            } catch (e) {}
          }
        });
      }
    };

    Object.extend(Ajax.Responders, Enumerable);

    Ajax.Responders.register({
      onCreate: function() {
        Ajax.activeRequestCount++;
      },

      onComplete: function() {
        Ajax.activeRequestCount--;
      }
    });

    /**
     * 我以為此時的Ajax對象起到命名空間的作用。
     * Ajax.Base 聲明為一個基礎對象類型
     * 注意 Ajax.Base 并沒有使用 Class.create() 的方式來創建,我想是因為作者并不希望 Ajax.Base 被庫使用者實例化。
     * 作者在其他對象類型的聲明中,將會繼承于它。
     * 就好像 java 中的私有抽象類
     */
    Ajax.Base = function() {};
    Ajax.Base.prototype = {
      setOptions: function(options) {
        this.options = {
          method:       'post',
          asynchronous: true,
          contentType:  'application/x-www-form-urlencoded',
          parameters:   ''
        }
        Object.extend(this.options, options || {});
      },

      responseIsSuccess: function() {
        return this.transport.status == undefined
            || this.transport.status == 0
            || (this.transport.status >= 200 && this.transport.status < 300);
      },

      responseIsFailure: function() {
        return !this.responseIsSuccess();
      }
    }

    /**
     * Ajax.Request 封裝 XmlHttp
     */
    Ajax.Request = Class.create();

    /**
     * 定義四種事件(狀態), 參考http://msdn.microsoft.com/workshop/author/dhtml/reference/properties/readystate_1.asp
     */
    Ajax.Request.Events =
      ['Uninitialized', 'Loading', 'Loaded', 'Interactive', 'Complete'];

    Ajax.Request.prototype = Object.extend(new Ajax.Base(), {
      initialize: function(url, options) {
        this.transport = Ajax.getTransport();
        this.setOptions(options);
        this.request(url);
      },

      request: function(url) {
        var parameters = this.options.parameters || '';
        if (parameters.length > 0) parameters += '&_=';

        try {
          this.url = url;
          if (this.options.method == 'get' && parameters.length > 0) this.url += (this.url.match(/\?/) ? '&' : '?') + parameters;

          Ajax.Responders.dispatch('onCreate', this, this.transport);

       /**
          * 此處好像強制使用了異步方式,而不是依照 this.options.asynchronous 的值
          */
          this.transport.open(this.options.method, this.url,
            this.options.asynchronous);

       /**
          * 這里提供了 XmlHttp 傳輸過程中每個步驟的回調函數
          */
          if (this.options.asynchronous) {
            this.transport.onreadystatechange = this.onStateChange.bind(this);
            setTimeout((function() {this.respondToReadyState(1)}).bind(this), 10);
          }

          this.setRequestHeaders();

          var body = this.options.postBody ? this.options.postBody : parameters;
          this.transport.send(this.options.method == 'post' ? body : null);

        } catch (e) {
          this.dispatchException(e);
        }
      },

      setRequestHeaders: function() {
        var requestHeaders =
          ['X-Requested-With', 'XMLHttpRequest',
           'X-Prototype-Version', Prototype.Version,
           'Accept', 'text/javascript, text/html, application/xml, text/xml, */*'];

        if (this.options.method == 'post') {
          requestHeaders.push('Content-type', this.options.contentType);

          if (this.transport.overrideMimeType)
            requestHeaders.push('Connection', 'close');
        }

        if (this.options.requestHeaders)
          requestHeaders.push.apply(requestHeaders, this.options.requestHeaders);

        for (var i = 0; i < requestHeaders.length; i += 2)
          this.transport.setRequestHeader(requestHeaders[i], requestHeaders[i+1]);
      },

      onStateChange: function() {
        var readyState = this.transport.readyState;
     /**
        * 如果不是 Loading 狀態,就調用回調函數
        */
        if (readyState != 1)
          this.respondToReadyState(this.transport.readyState);
      },

      header: function(name) {
        try {
          return this.transport.getResponseHeader(name);
        } catch (e) {}
      },

      evalJSON: function() {
        try {
          return eval('(' + this.header('X-JSON') + ')');
        } catch (e) {}
      }, evalResponse: function() {
        try {
          return eval(this.transport.responseText);
        } catch (e) {
          this.dispatchException(e);
        }
      },

      /**
       * 回調函數定義在 this.options 屬性中,比如:
          var option = {
             onLoaded : function(req) {...};
             ......
          }
          new Ajax.Request(url, option);
       */
      respondToReadyState: function(readyState) {
        var event = Ajax.Request.Events[readyState];
        var transport = this.transport, json = this.evalJSON();

        if (event == 'Complete') {
          try {
            (this.options['on' + this.transport.status]
             || this.options['on' + (this.responseIsSuccess() ? 'Success' : 'Failure')]
             || Prototype.emptyFunction)(transport, json);
          } catch (e) {
            this.dispatchException(e);
          }

          if ((this.header('Content-type') || '').match(/^text\/javascript/i))
            this.evalResponse();
        }

        try {
          (this.options['on' + event] || Prototype.emptyFunction)(transport, json);
          Ajax.Responders.dispatch('on' + event, this, transport, json);
        } catch (e) {
          this.dispatchException(e);
        }

        if (event == 'Complete')
          this.transport.onreadystatechange = Prototype.emptyFunction;
      },

      dispatchException: function(exception) {
        (this.options.onException || Prototype.emptyFunction)(this, exception);
        Ajax.Responders.dispatch('onException', this, exception);
      }
    });

    /**
     * Ajax.Updater 用于綁定一個html元素與 XmlHttp調用的返回值。類似與 buffalo 的 bind。
     * 如果 options 中有 insertion(from dom.js) 對象的話, insertion 能提供更多的插入控制。
     */
    Ajax.Updater = Class.create();

    Object.extend(Object.extend(Ajax.Updater.prototype, Ajax.Request.prototype), {
      initialize: function(container, url, options) {
        this.containers = {
          success: container.success ? $(container.success) : $(container),
          failure: container.failure ? $(container.failure) :
            (container.success ? null : $(container))
        }

        this.transport = Ajax.getTransport();
        this.setOptions(options);var onComplete = this.options.onComplete || Prototype.emptyFunction;
        this.options.onComplete = (function(transport, object) {
          this.updateContent();
          onComplete(transport, object);
        }).bind(this);

        this.request(url);
      },

      updateContent: function() {
        var receiver = this.responseIsSuccess() ?
          this.containers.success : this.containers.failure;
        var response = this.transport.responseText;

        if (!this.options.evalScripts)
          response = response.stripScripts();

        if (receiver) {
          if (this.options.insertion) {
            new this.options.insertion(receiver, response);
          } else {
            Element.update(receiver, response);
          }
        }

        if (this.responseIsSuccess()) {
          if (this.onComplete)
            setTimeout(this.onComplete.bind(this), 10);
        }
      }
    });

    Ajax.PeriodicalUpdater = Class.create();
    Ajax.PeriodicalUpdater.prototype = Object.extend(new Ajax.Base(), {
      initialize: function(container, url, options) {
        this.setOptions(options);
        this.onComplete = this.options.onComplete;

        this.frequency = (this.options.frequency || 2);
        this.decay = (this.options.decay || 1);

        this.updater = {};
        this.container = container;
        this.url = url;

        this.start();
      },

      start: function() {
        this.options.onComplete = this.updateComplete.bind(this);
        this.onTimerEvent();
      },

      stop: function() {
        this.updater.onComplete = undefined;
        clearTimeout(this.timer);
        (this.onComplete || Prototype.emptyFunction).apply(this, arguments);
      },

      updateComplete: function(request) {
        if (this.options.decay) {
          this.decay = (request.responseText == this.lastText ?
            this.decay * this.options.decay : 1);

          this.lastText = request.responseText;
        }
        this.timer = setTimeout(this.onTimerEvent.bind(this),
          this.decay * this.frequency * 1000);
      },

      onTimerEvent: function() {
        this.updater = new Ajax.Updater(this.container, this.url, this.options);
      }
    });

    /**
     * 這個函數就 Ruby 了。我覺得它的作用主要有兩個
     * 1.  大概是 document.getElementById(id) 的最簡化調用。
     * 比如:$("aaa") 將返回上 aaa 對象  * 2.  得到對象數組
     * 比如: $("aaa","bbb") 返回一個包括id為"aaa"和"bbb"兩個input控件對象的數組。
     */
    function $() {
      var results = [], element;
      for (var i = 0; i < arguments.length; i++) {
        element = arguments[i];
        if (typeof element == 'string')
          element = document.getElementById(element);
        results.push(Element.extend(element));
      }
      return results.length < 2 ? results[0] : results;
    }

    document.getElementsByClassName = function(className, parentElement) {
      var children = ($(parentElement) || document.body).getElementsByTagName('*');
      return $A(children).inject([], function(elements, child) {
        if (child.className.match(new RegExp("(^|\\s)" + className + "(\\s|$)")))
          elements.push(Element.extend(child));
        return elements;
      });
    }

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

    if (!window.Element)
      var Element = new Object();

    Element.extend = function(element) {
      if (!element) return;
      if (_nativeExtensions) return element;

      if (!element._extended && element.tagName && element != window) {
        var methods = Element.Methods, cache = Element.extend.cache;
        for (property in methods) {
          var value = methods[property];
          if (typeof value == 'function')
            element[property] = cache.findOrStore(value);
        }
      }

      element._extended = true;
      return element;
    }

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

    Element.Methods = {
      visible: function(element) {
        return $(element).style.display != 'none';
      },

      toggle: function() {
        for (var i = 0; i < arguments.length; i++) {
          var element = $(arguments[i]);
          Element[Element.visible(element) ? 'hide' : 'show'](element);
        }
      },

      hide: function() {
        for (var i = 0; i < arguments.length; i++) {
          var element = $(arguments[i]);
          element.style.display = 'none';
        }
      },

      show: function() {
        for (var i = 0; i < arguments.length; i++) {
          var element = $(arguments[i]);
          element.style.display = '';
        }
      },

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

      update: function(element, html) { $(element).innerHTML = html.stripScripts();
        setTimeout(function() {html.evalScripts()}, 10);
      },

      replace: function(element, html) {
        element = $(element);
        if (element.outerHTML) {
          element.outerHTML = html.stripScripts();
        } else {
          var range = element.ownerDocument.createRange();
          range.selectNodeContents(element);
          element.parentNode.replaceChild(
            range.createContextualFragment(html.stripScripts()), element);
        }
        setTimeout(function() {html.evalScripts()}, 10);
      },

      getHeight: function(element) {
        element = $(element);
        return element.offsetHeight;
      },

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

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

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

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

      // removes whitespace-only text node children
      cleanWhitespace: function(element) {
        element = $(element);
        for (var i = 0; i < element.childNodes.length; i++) {
          var node = element.childNodes[i];
          if (node.nodeType == 3 && !/\S/.test(node.nodeValue))
            Element.remove(node);
        }
      },

      empty: function(element) {
        return $(element).innerHTML.match(/^\s*$/);
      },

      childOf: function(element, ancestor) {
        element = $(element), ancestor = $(ancestor);
        while (element = element.parentNode)
          if (element == ancestor) return true;
        return false;
      },

      scrollTo: function(element) {
        element = $(element);
        var x = element.x ? element.x : element.offsetLeft,
            y = element.y ? element.y : element.offsetTop;
        window.scrollTo(x, y);
      },

      getStyle: function(element, style) {
        element = $(element);
        var value = element.style[style.camelize()];
        if (!value) {
          if (document.defaultView && document.defaultView.getComputedStyle) {
            var css = document.defaultView.getComputedStyle(element, null); value = css ? css.getPropertyValue(style) : null;
          } else if (element.currentStyle) {
            value = element.currentStyle[style.camelize()];
          }
        }

        if (window.opera && ['left', 'top', 'right', 'bottom'].include(style))
          if (Element.getStyle(element, 'position') == 'static') value = 'auto';

        return value == 'auto' ? null : value;
      },

      setStyle: function(element, style) {
        element = $(element);
        for (var name in style)
          element.style[name.camelize()] = style[name];
      },

      getDimensions: function(element) {
        element = $(element);
        if (Element.getStyle(element, 'display') != 'none')
          return {width: element.offsetWidth, height: element.offsetHeight};

        var els = element.style;
        var originalVisibility = els.visibility;
        var originalPosition = els.position;
        els.visibility = 'hidden';
        els.position = 'absolute';
        els.display = '';
        var originalWidth = element.clientWidth;
        var originalHeight = element.clientHeight;
        els.display = 'none';
        els.position = originalPosition;
        els.visibility = originalVisibility;
        return {width: originalWidth, height: originalHeight};
      },

      makePositioned: function(element) {
        element = $(element);
        var pos = Element.getStyle(element, 'position');
        if (pos == 'static' || !pos) {
          element._madePositioned = true;
          element.style.position = 'relative';
          if (window.opera) {
            element.style.top = 0;
            element.style.left = 0;
          }
        }
      },

      undoPositioned: function(element) {
        element = $(element);
        if (element._madePositioned) {
          element._madePositioned = undefined;
          element.style.position =
            element.style.top =
            element.style.left =
            element.style.bottom =
            element.style.right = '';
        }
      },

      makeClipping: function(element) {
        element = $(element);
        if (element._overflow) return;
        element._overflow = element.style.overflow;
        if ((Element.getStyle(element, 'overflow') || 'visible') != 'hidden') element.style.overflow = 'hidden';
      },

      undoClipping: function(element) {
        element = $(element);
        if (element._overflow) return;
        element.style.overflow = element._overflow;
        element._overflow = undefined;
      }
    }

    Object.extend(Element, Element.Methods);

    var _nativeExtensions = false;

    if(!HTMLElement && /Konqueror|Safari|KHTML/.test(navigator.userAgent)) {
      var HTMLElement = {}
      HTMLElement.prototype = document.createElement('div').__proto__;
    }

    Element.addMethods = function(methods) {
      Object.extend(Element.Methods, methods || {});

      if(typeof HTMLElement != 'undefined') {
        var methods = Element.Methods, cache = Element.extend.cache;
        for (property in methods) {
          var value = methods[property];
          if (typeof value == 'function')
            HTMLElement.prototype[property] = cache.findOrStore(value);
        }
        _nativeExtensions = true;
      }
    }

    Element.addMethods();

    var Toggle = new Object();
    Toggle.display = Element.toggle;

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

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

    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.toLowerCase();
            if (tagName == 'tbody' || tagName == 'tr') {
              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);
      },

      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(this.toArray().concat(classNameToAdd).join(' '));
      },

      remove: function(classNameToRemove) {
        if (!this.include(classNameToRemove)) return;
        this.set(this.select(function(className) {
          return className != classNameToRemove;
        }).join(' '));},

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

    Object.extend(Element.ClassNames.prototype, Enumerable);
    var Selector = Class.create();
    Selector.prototype = {
      initialize: function(expression) {
        this.params = {classNames: []};
        this.expression = expression.toString().strip();
        this.parseExpression();
        this.compileMatcher();
      },

      parseExpression: function() {
        function abort(message) { throw 'Parse error in selector: ' + message; }

        if (this.expression == '')  abort('empty expression');

        var params = this.params, expr = this.expression, match, modifier, clause, rest;
        while (match = expr.match(/^(.*)\[([a-z0-9_:-]+?)(?:([~\|!]?=)(?:"([^"]*)"|([^\]\s]*)))?\]$/i)) {
          params.attributes = params.attributes || [];
          params.attributes.push({name: match[2], operator: match[3], value: match[4] || match[5] || ''});
          expr = match[1];
        }

        if (expr == '*') return this.params.wildcard = true;

        while (match = expr.match(/^([^a-z0-9_-])?([a-z0-9_-]+)(.*)/i)) {
          modifier = match[1], clause = match[2], rest = match[3];
          switch (modifier) {
            case '#':       params.id = clause; break;
            case '.':       params.classNames.push(clause); break;
            case '':
            case undefined: params.tagName = clause.toUpperCase(); break;
            default:        abort(expr.inspect());
          }
          expr = rest;
        }

        if (expr.length > 0) abort(expr.inspect());
      },

      buildMatchExpression: function() {
        var params = this.params, conditions = [], clause;

        if (params.wildcard)
          conditions.push('true');
        if (clause = params.id)
          conditions.push('element.id == ' + clause.inspect());
        if (clause = params.tagName)
          conditions.push('element.tagName.toUpperCase() == ' + clause.inspect());
        if ((clause = params.classNames).length > 0)
          for (var i = 0; i < clause.length; i++)
            conditions.push('Element.hasClassName(element, ' + clause[i].inspect() + ')');
        if (clause = params.attributes) {
          clause.each(function(attribute) {
            var value = 'element.getAttribute(' + attribute.name.inspect() + ')';var splitValueBy = function(delimiter) {
              return value + ' && ' + value + '.split(' + delimiter.inspect() + ')';
            }

            switch (attribute.operator) {
              case '=':       conditions.push(value + ' == ' + attribute.value.inspect()); break;
              case '~=':      conditions.push(splitValueBy(' ') + '.include(' + attribute.value.inspect() + ')'); break;
              case '|=':      conditions.push(
                                splitValueBy('-') + '.first().toUpperCase() == ' + attribute.value.toUpperCase().inspect()
                              ); break;
              case '!=':      conditions.push(value + ' != ' + attribute.value.inspect()); break;
              case '':
              case undefined: conditions.push(value + ' != null'); break;
              default:        throw 'Unknown operator ' + attribute.operator + ' in selector';
            }
          });
        }

        return conditions.join(' && ');
      },

      compileMatcher: function() {
        this.match = new Function('element', 'if (!element.tagName) return false; \
          return ' + this.buildMatchExpression());
      },

      findElements: function(scope) {
        var element;

        if (element = $(this.params.id))
          if (this.match(element))
            if (!scope || Element.childOf(element, scope))
              return [element];

        scope = (scope || document).getElementsByTagName(this.params.tagName || '*');

        var results = [];
        for (var i = 0; i < scope.length; i++)
          if (this.match(element = scope[i]))
            results.push(Element.extend(element));

        return results;
      },

      toString: function() {
        return this.expression;
      }
    }

    function $$() {
      return $A(arguments).map(function(expression) {
        return expression.strip().split(/\s+/).inject([null], function(results, expr) { var selector = new Selector(expr);
          return results.map(selector.findElements.bind(selector)).flatten();
        });
      }).flatten();
    }

    /**
     * 針對 頁面元素對象 的工具類,提供一些簡單靜態方法
     */
    var Field = {
     /**
       * 清除參數引用對象的值
       */
      clear: function() {
        for (var i = 0; i < arguments.length; i++)
          $(arguments[i]).value = '';
      },

      /**
       * 使參數引用對象獲取焦點
       */
      focus: function(element) {
        $(element).focus();
      },

      /**
       * 判斷參數引用對象值是否為空,如為空,返回false, 反之true
       */
      present: function() {
        for (var i = 0; i < arguments.length; i++)
          if ($(arguments[i]).value == '') return false;
        return true;
      },

      /**
       * 使選中參數引用對象
       */
      select: function(element) {
        $(element).select();
      },

      /**
       * 使參數引用對象處于可編輯狀態
       */
      activate: function(element) {
        element = $(element);
        element.focus();
        if (element.select)
          element.select();
      }
    }

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

    /**
     * 表單工具類
     */
    var Form = {
     /**
       * 將表單元素序列化后的值組合成 QueryString 的形式
       */
      serialize: function(form) {
        var elements = Form.getElements($(form));
        var queryComponents = new Array();

        for (var i = 0; i < elements.length; i++) {
          var queryComponent = Form.Element.serialize(elements[i]);
          if (queryComponent)
            queryComponents.push(queryComponent);
        }

        return queryComponents.join('&');
      },

      /**
       * 得到表單的所有元素對象
       */
      getElements: function(form) {
        form = $(form);
        var elements = new Array();

        for (var tagName in Form.Element.Serializers) {
          var tagElements = form.getElementsByTagName(tagName);
          for (var j = 0; j < tagElements.length; j++)
            elements.push(tagElements[j]);
        }
        return elements;
      },

      getInputs: function(form, typeName, name) {
        form = $(form);
        var inputs = form.getElementsByTagName('input');

        if (!typeName && !name)
          return inputs;

        var matchingInputs = new Array();
        for (var i = 0; i < inputs.length; i++) { var input = inputs[i];
          if ((typeName && input.type != typeName) ||
              (name && input.name != name))
            continue;
          matchingInputs.push(input);
        }

        return matchingInputs;
      },

      /**
       * 將指定表單的元素置于不可用狀態
       */
      disable: function(form) {
        var elements = Form.getElements(form);
        for (var i = 0; i < elements.length; i++) {
          var element = elements[i];
          element.blur();
          element.disabled = 'true';
        }
      },

      enable: function(form) {
        var elements = Form.getElements(form);
        for (var i = 0; i < elements.length; i++) {
          var element = elements[i];
          element.disabled = '';
        }
      },

      findFirstElement: function(form) {
        return Form.getElements(form).find(function(element) {
          return element.type != 'hidden' && !element.disabled &&
            ['input', 'select', 'textarea'].include(element.tagName.toLowerCase());
        });
      },

      /**
       * 使表單的第一個非 hidden 類型而且處于可用狀態的元素獲得焦點
       */
      focusFirstElement: function(form) {
        Field.activate(Form.findFirstElement(form));
      },

      /*
       * 重置表單
       */
      reset: function(form) {
        $(form).reset();
      }
    }

    /**
     * 表單元素工具類
     */
    Form.Element = {
      /**
       * 返回表單元素的值先序列化再進行 URL 編碼后的值
       */
      serialize: function(element) {
        element = $(element);
        var method = element.tagName.toLowerCase();
        var parameter = Form.Element.Serializers[method](element);

        if (parameter) {
          var key = encodeURIComponent(parameter[0]);
          if (key.length == 0) return;

          if (parameter[1].constructor != Array)
            parameter[1] = [parameter[1]];

          return parameter[1].map(function(value) {
            return key + '=' + encodeURIComponent(value);
          }).join('&');
        }
      },

      /**
       *  返回表單元素序列化后的值
       */
      getValue: function(element) {
        element = $(element);
        var method = element.tagName.toLowerCase();
        var parameter = Form.Element.Serializers[method](element);if (parameter)
          return parameter[1];
      }
    }

    /**
     * prototype 的所謂序列化其實就是將表單的名字和值組合成一個數組
     */
    Form.Element.Serializers = {
      input: function(element) {
        switch (element.type.toLowerCase()) {
          case 'submit':
          case 'hidden':
          case 'password':
          case 'text':
            return Form.Element.Serializers.textarea(element);
          case 'checkbox':
          case 'radio':
            return Form.Element.Serializers.inputSelector(element);
        }
        return false;
      },

      inputSelector: function(element) {
        if (element.checked)
          return [element.name, element.value];
      },

      textarea: function(element) {
        return [element.name, element.value];
      },

      select: function(element) {
        return Form.Element.Serializers[element.type == 'select-one' ?
          'selectOne' : 'selectMany'](element);
      },

      selectOne: function(element) {
        var value = '', opt, index = element.selectedIndex;
        if (index >= 0) {
          opt = element.options[index];
          value = opt.value || opt.text;
        }
        return [element.name, value];
      },

      selectMany: function(element) {
        var value = [];
        for (var i = 0; i < element.length; i++) {
          var opt = element.options[i];
          if (opt.selected)
            value.push(opt.value || opt.text);
        }
        return [element.name, value];
      }
    }

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

    var $F = Form.Element.getValue;

    /*--------------------------------------------------------------------------*/
    /**
     * Abstract.TimedObserver 也沒有用 Class.create() 來創建,和Ajax.Base 意圖應該一樣
     * Abstract.TimedObserver 顧名思義,是套用Observer設計模式來跟蹤指定表單元素,
     * 當表單元素的值發生變化的時候,就執行回調函數
     *
     * 我想 Observer 與注冊onchange事件相似,不同點在于 onchange 事件是在元素失去焦點的時候才激發。
     * 同樣的與 onpropertychange 事件也相似,不過它只關注表單元素的值的變化,而且提供timeout的控制。
     *
     * 除此之外,Observer 的好處大概就在與更面向對象,另外可以動態的更換回調函數,這就比注冊事件要靈活一些。
     * Observer 應該可以勝任動態數據校驗,或者多個關聯下拉選項列表的連動等等
     *
     */
    Abstract.TimedObserver = function() {}
    Abstract.TimedObserver.prototype = {
      initialize: function(element, frequency, callback) {  this.frequency = frequency;
        this.element   = $(element);
        this.callback  = callback;

        this.lastValue = this.getValue();
        this.registerCallback();
      },

      registerCallback: function() {
        setInterval(this.onTimerEvent.bind(this), this.frequency * 1000);
      },

      onTimerEvent: function() {
        var value = this.getValue();
        if (this.lastValue != value) {
          this.callback(this.element, value);
          this.lastValue = value;
        }
      }
    }

    Form.Element.Observer = Class.create();
    Form.Element.Observer.prototype = Object.extend(new Abstract.TimedObserver(), {
      getValue: function() {
        return Form.Element.getValue(this.element);
      }
    });

    Form.Observer = Class.create();
    Form.Observer.prototype = Object.extend(new Abstract.TimedObserver(), {
      getValue: function() {
        return Form.serialize(this.element);
      }
    });

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

    Abstract.EventObserver = function() {}
    Abstract.EventObserver.prototype = {
      initialize: function(element, callback) {
        this.element  = $(element);
        this.callback = callback;

        this.lastValue = this.getValue();
        if (this.element.tagName.toLowerCase() == 'form')
          this.registerFormCallbacks();
        else
          this.registerCallback(this.element);
      },

      onElementEvent: function() {
        var value = this.getValue();
        if (this.lastValue != value) {
          this.callback(this.element, value);
          this.lastValue = value;
        }
      },

      registerFormCallbacks: function() {
        var elements = Form.getElements(this.element);
        for (var i = 0; i < elements.length; i++)
          this.registerCallback(elements[i]);
      },

      registerCallback: function(element) {
        if (element.type) {
          switch (element.type.toLowerCase()) {
            case 'checkbox':
            case 'radio':
              Event.observe(element, 'click', this.onElementEvent.bind(this));
              break;
            case 'password':
            case 'text':
            case 'textarea':
            case 'select-one':
            case 'select-multiple':
              Event.observe(element, 'change', this.onElementEvent.bind(this)); break;
          }
        }
      }
    }

    Form.Element.EventObserver = Class.create();
    Form.Element.EventObserver.prototype = Object.extend(new Abstract.EventObserver(), {
      getValue: function() {
        return Form.Element.getValue(this.element);
      }
    });

    Form.EventObserver = Class.create();
    Form.EventObserver.prototype = Object.extend(new Abstract.EventObserver(), {
      getValue: function() {
        return Form.serialize(this.element);
      }
    });
    if (!window.Event) {
      var Event = new Object();
    }

    Object.extend(Event, {
      KEY_BACKSPACE: 8,
      KEY_TAB:       9,
      KEY_RETURN:   13,
      KEY_ESC:      27,
      KEY_LEFT:     37,
      KEY_UP:       38,
      KEY_RIGHT:    39,
      KEY_DOWN:     40,
      KEY_DELETE:   46,

      element: function(event) {
        return event.target || event.srcElement;
      },

      isLeftClick: function(event) {
        return (((event.which) && (event.which == 1)) ||
                ((event.button) && (event.button == 1)));
      },

      pointerX: function(event) {
        return event.pageX || (event.clientX +
          (document.documentElement.scrollLeft || document.body.scrollLeft));
      },

      pointerY: function(event) {
        return event.pageY || (event.clientY +
          (document.documentElement.scrollTop || document.body.scrollTop));
      },

      stop: function(event) {
        if (event.preventDefault) {
          event.preventDefault();
          event.stopPropagation();
        } else {
          event.returnValue = false;
          event.cancelBubble = true;
        }
      },

      findElement: function(event, tagName) {
        var element = Event.element(event);
        while (element.parentNode && (!element.tagName ||
            (element.tagName.toUpperCase() != tagName.toUpperCase())))
          element = element.parentNode;
        return element;
      },

      observers: false,

      _observeAndCache: function(element, name, observer, useCapture) {
        if (!this.observers) this.observers = [];
        if (element.addEventListener) {
          this.observers.push([element, name, observer, useCapture]);
          element.addEventListener(name, observer, useCapture);
        } else if (element.attachEvent) {
          this.observers.push([element, name, observer, useCapture]);


          element.attachEvent('on' + name, observer);
        }
      },

      unloadCache: function() {
        if (!Event.observers) return;
        for (var i = 0; i < Event.observers.length; i++) {
          Event.stopObserving.apply(this, Event.observers[i]);
          Event.observers[i][0] = null;
        }
        Event.observers = false;
      },

      observe: function(element, name, observer, useCapture) {
        var element = $(element);
        useCapture = useCapture || false;

        if (name == 'keypress' &&
            (navigator.appVersion.match(/Konqueror|Safari|KHTML/)
            || element.attachEvent))
          name = 'keydown';

        this._observeAndCache(element, name, observer, useCapture);
      },

      stopObserving: function(element, name, observer, useCapture) {
        var element = $(element);
        useCapture = useCapture || false;

        if (name == 'keypress' &&
            (navigator.appVersion.match(/Konqueror|Safari|KHTML/)
            || element.detachEvent))
          name = 'keydown';

        if (element.removeEventListener) {
          element.removeEventListener(name, observer, useCapture);
        } else if (element.detachEvent) {
          element.detachEvent('on' + name, observer);
        }
      }
    });

    /* prevent memory leaks in IE */
    if (navigator.appVersion.match(/\bMSIE\b/))
      Event.observe(window, 'unload', Event.unloadCache, false);
    var Position = {
      includeScrollOffsets: false,

      prepare: function() {
        this.deltaX =  window.pageXOffset
                    || document.documentElement.scrollLeft
                    || document.body.scrollLeft
                    || 0;
        this.deltaY =  window.pageYOffset
                    || document.documentElement.scrollTop
                    || document.body.scrollTop
                    || 0;
      },

      realOffset: function(element) {
        var valueT = 0, valueL = 0;
        do {
          valueT += element.scrollTop  || 0;
          valueL += element.scrollLeft || 0;
          element = element.parentNode; } while (element);
        return [valueL, valueT];
      },

      cumulativeOffset: function(element) {
        var valueT = 0, valueL = 0;
        do {
          valueT += element.offsetTop  || 0;
          valueL += element.offsetLeft || 0;
          element = element.offsetParent;
        } while (element);
        return [valueL, valueT];
      },

      positionedOffset: function(element) {
        var valueT = 0, valueL = 0;
        do {
          valueT += element.offsetTop  || 0;
          valueL += element.offsetLeft || 0;
          element = element.offsetParent;
          if (element) {
            p = Element.getStyle(element, 'position');
            if (p == 'relative' || p == 'absolute') break;
          }
        } while (element);
        return [valueL, valueT];
      },

      offsetParent: function(element) {
        if (element.offsetParent) return element.offsetParent;
        if (element == document.body) return element;

        while ((element = element.parentNode) && element != document.body)
          if (Element.getStyle(element, 'position') != 'static')
            return element;

        return document.body;
      },

      within: function(element, x, y) {
        if (this.includeScrollOffsets)
          return this.withinIncludingScrolloffsets(element, x, y);
        this.xcomp = x;
        this.ycomp = y;
        this.offset = this.cumulativeOffset(element);

        return (y >= this.offset[1] &&
                y <  this.offset[1] + element.offsetHeight &&
                x >= this.offset[0] &&
                x <  this.offset[0] + element.offsetWidth);
      },

      withinIncludingScrolloffsets: function(element, x, y) {
        var offsetcache = this.realOffset(element);

        this.xcomp = x + offsetcache[0] - this.deltaX;
        this.ycomp = y + offsetcache[1] - this.deltaY;
        this.offset = this.cumulativeOffset(element);

        return (this.ycomp >= this.offset[1] &&
                this.ycomp <  this.offset[1] + element.offsetHeight &&
                this.xcomp >= this.offset[0] &&  },

      overlap: function(mode, element) {
        if (!mode) return 0;
        if (mode == 'vertical')
          return ((this.offset[1] + element.offsetHeight) - this.ycomp) /
            element.offsetHeight;
        if (mode == 'horizontal')
          return ((this.offset[0] + element.offsetWidth) - this.xcomp) /
            element.offsetWidth;
      },

      clone: function(source, target) {
        source = $(source);
        target = $(target);
        target.style.position = 'absolute';
        var offsets = this.cumulativeOffset(source);
        target.style.top    = offsets[1] + 'px';
        target.style.left   = offsets[0] + 'px';
        target.style.width  = source.offsetWidth + 'px';
        target.style.height = source.offsetHeight + 'px';
      },

      page: function(forElement) {
        var valueT = 0, valueL = 0;

        var element = forElement;
        do {
          valueT += element.offsetTop  || 0;
          valueL += element.offsetLeft || 0;

          if (element.offsetParent==document.body)
            if (Element.getStyle(element,'position')=='absolute') break;

        } while (element = element.offsetParent);

        element = forElement;
        do {
          valueT -= element.scrollTop  || 0;
          valueL -= element.scrollLeft || 0;
        } while (element = element.parentNode);

        return [valueL, valueT];
      },

      clone: function(source, target) {
        var options = Object.extend({
          setLeft:    true,
          setTop:     true,
          setWidth:   true,
          setHeight:  true,
          offsetTop:  0,
          offsetLeft: 0
        }, arguments[2] || {})

        // find page position of source
        source = $(source);
        var p = Position.page(source);

        target = $(target);
        var delta = [0, 0];
        var parent = null;
        if (Element.getStyle(target,'position') == 'absolute') {
          parent = Position.offsetParent(target);
          delta = Position.page(parent);
        }

        if (parent == document.body) {
          delta[0] -= document.body.offsetLeft;
          delta[1] -= document.body.offsetTop;
        }

    if(options.setLeft)   target.style.left  = (p[0] - delta[0] + options.offsetLeft) + 'px';
        if(options.setTop)    target.style.top   = (p[1] - delta[1] + options.offsetTop) + 'px';
        if(options.setWidth)  target.style.width = source.offsetWidth + 'px';
        if(options.setHeight) target.style.height = source.offsetHeight + 'px';
      },

      absolutize: function(element) {
        element = $(element);
        if (element.style.position == 'absolute') return;
        Position.prepare();

        var offsets = Position.positionedOffset(element);
        var top     = offsets[1];
        var left    = offsets[0];
        var width   = element.clientWidth;
        var height  = element.clientHeight;

        element._originalLeft   = left - parseFloat(element.style.left  || 0);
        element._originalTop    = top  - parseFloat(element.style.top || 0);
        element._originalWidth  = element.style.width;
        element._originalHeight = element.style.height;

        element.style.position = 'absolute';
        element.style.top    = top + 'px';;
        element.style.left   = left + 'px';;
        element.style.width  = width + 'px';;
        element.style.height = height + 'px';;
      },

      relativize: function(element) {
        element = $(element);
        if (element.style.position == 'relative') return;
        Position.prepare();

        element.style.position = 'relative';
        var top  = parseFloat(element.style.top  || 0) - (element._originalTop || 0);
        var left = parseFloat(element.style.left || 0) - (element._originalLeft || 0);

        element.style.top    = top + 'px';
        element.style.left   = left + 'px';
        element.style.height = element._originalHeight;
        element.style.width  = element._originalWidth;
      }
    }

    if (/Konqueror|Safari|KHTML/.test(navigator.userAgent)) {
      Position.cumulativeOffset = function(element) {
        var valueT = 0, valueL = 0;
        do {
          valueT += element.offsetTop  || 0;
          valueL += element.offsetLeft || 0;
          if (element.offsetParent == document.body)
            if (Element.getStyle(element, 'position') == 'absolute') break;

          element = element.offsetParent;
        } while (element);

        return [valueL, valueT];
      }
    }

    var SelectorLiteAddon=Class.create();


                this.xcomp <  this.offset[0] + element.offsetWidth);SelectorLiteAddon.prototype = {

      initialize: function(stack) {
       
        this.r=[]; //results
        this.s=[]; //stack of selectors
        this.i=0;  //stack pointer
       
        for (var i=stack.length-1;i>=0;i--) {
       
          var s=["*","",[]];
         
          var t=stack[i];
         
          var cursor=t.length-1;
          do {
           
            var d=t.lastIndexOf("#");
            var p=t.lastIndexOf(".");
            cursor=Math.max(d,p);
           
            if (cursor==-1) {
              s[0]=t.toUpperCase();
             
            } else if (d==-1 || p==cursor) {
              s[2].push(t.substring(p+1));
             
            } else if (!s[1]) {
              s[1]=t.substring(d+1);
            }
            t=t.substring(0,cursor);
          } while (cursor>0);
          this.s[i]=s;
        }
      },
     
      get:function(root) {
        this.explore(root || document,this.i==(this.s.length-1));
        return this.r;
      },
     
      explore:function(elt,leaf) {
       
        var s=this.s[this.i];
       
        var r=[];
       
        if (s[1]) {
       
          e=$(s[1]);     
          if (e && (s[0]=="*" || e.tagName==s[0]) && e.childOf(elt)) {
           r=[e];
          }
         
        } else {
          r=$A(elt.getElementsByTagName(s[0]));
        }
       
        if (s[2].length==1) { //single classname
          r=r.findAll(function(o) {
         
            if (o.className.indexOf(" ")==-1) {
              return o.className==s[2][0];
            } else {
              return o.className.split(/\s+/).include(s[2][0]);
            }
          });
       
        } else if (s[2].length>0) {  r=r.findAll(function(o) {
         
            if (o.className.indexOf(" ")==-1) {
              return false;
            } else {
           
              var q=o.className.split(/\s+/);
              return s[2].all(function(c) {
                return q.include(c);
              });
            }
          });
        }
       
       
        if (leaf) {
          this.r=this.r.concat(r);
         
        } else {
          ++this.i;
          r.each(function(o) {
            this.explore(o,this.i==(this.s.length-1));
          }.bind(this));
        }
      }
     
    }


    var $$old=$$;

    var $$=function(a,b) {

      if (b || a.indexOf("[")>=0) return $$old.apply(this,arguments);
     
      return new SelectorLiteAddon(a.split(/\s+/)).get();
    }


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