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          prototype.js 1.4 原代碼閱讀

          Posted on 2007-05-11 23:05 snowolf 閱讀(348) 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??梢砸黄鹧芯肯?。
           */
          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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