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IE中getter/setter 的实现
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>A Crazy Getter/Setter Hack</title> | |
| </head> | |
| <body> | |
| <ul> | |
| <li>Object.defineProperty API：https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty</li> | |
| <li>https://github.com/RubyLouvre/avalon/blob/master/avalon.shim.js#L1394</li> | |
| <li>https://gist.github.com/jeffrafter/189354</li> | |
| <li>http://download.dojotoolkit.org/release-1.9.7/dojo-release-1.9.7/dojox/lang/observable.js.uncompressed.js</li> | |
| </ul> | |
| <pre> | |
| 通过vbscript来hack的方式勉强可用，不过有以下缺点：（https://github.com/migijs/migi/issues/5#issuecomment-103778075） | |
| 1. vbscript是不区分大小写的 | |
| 2. vbscript不能增删属性，所以每次需重新定义class，实现上麻烦且bug，且无法确保如delete之类的语义 | |
| 3. 性能糟糕 | |
| 4. 很大的内存泄漏风险（因为vbscript的垃圾回收机制是计数） | |
| </pre> | |
| <script type="text/javascript"> | |
| var defineProperty = Object.defineProperty | |
| var canHideOwn = true | |
| //如果浏览器不支持ecma262v5的Object.defineProperties或者存在BUG，比如IE8 | |
| //标准浏览器使用__defineGetter__, __defineSetter__实现 | |
| try { | |
| defineProperty({}, "_", { | |
| value: "x" | |
| }) | |
| var defineProperties = Object.defineProperties | |
| } catch (e) { | |
| canHideOwn = false | |
| } | |
| if (!canHideOwn) { | |
| if ("__defineGetter__" in avalon) { | |
| defineProperty = function (obj, prop, desc) { | |
| if ('value' in desc) { | |
| obj[prop] = desc.value | |
| } | |
| if ("get" in desc) { | |
| obj.__defineGetter__(prop, desc.get) | |
| } | |
| if ('set' in desc) { | |
| obj.__defineSetter__(prop, desc.set) | |
| } | |
| return obj | |
| } | |
| defineProperties = function (obj, descs) { | |
| for (var prop in descs) { | |
| if (descs.hasOwnProperty(prop)) { | |
| defineProperty(obj, prop, descs[prop]) | |
| } | |
| } | |
| return obj | |
| } | |
| } | |
| if (IEVersion) { | |
| window.execScript([ // jshint ignore:line | |
| "Function parseVB(code)", | |
| "\tExecuteGlobal(code)", | |
| "End Function", | |
| "Dim VBClassBodies", | |
| "Set VBClassBodies=CreateObject(\"Scripting.Dictionary\")", | |
| "Function findOrDefineVBClass(name,body)", | |
| "\tDim found", | |
| "\tfound=\"\"", | |
| "\tFor Each key in VBClassBodies", | |
| "\t\tIf body=VBClassBodies.Item(key) Then", | |
| "\t\t\tfound=key", | |
| "\t\t\tExit For", | |
| "\t\tEnd If", | |
| "\tnext", | |
| "\tIf found=\"\" Then", | |
| "\t\tparseVB(\"Class \" + name + body)", | |
| "\t\tVBClassBodies.Add name, body", | |
| "\t\tfound=name", | |
| "\tEnd If", | |
| "\tfindOrDefineVBClass=found", | |
| "End Function" | |
| ].join("\n"), "VBScript") | |
| function VBMediator(instance, accessors, name, value) {// jshint ignore:line | |
| var accessor = accessors[name] | |
| if (arguments.length === 4) { | |
| accessor.call(instance, value) | |
| } else { | |
| return accessor.call(instance) | |
| } | |
| } | |
| defineProperties = function (name, accessors, properties) { | |
| var className = "VBClass" + setTimeout("1"),// jshint ignore:line | |
| buffer = [] | |
| buffer.push( | |
| "\r\n\tPrivate [__data__], [__proxy__]", | |
| "\tPublic Default Function [__const__](d, p)", | |
| "\t\tSet [__data__] = d: set [__proxy__] = p", | |
| "\t\tSet [__const__] = Me", //链式调用 | |
| "\tEnd Function") | |
| //添加普通属性,因为VBScript对象不能像JS那样随意增删属性，必须在这里预先定义好 | |
| for (name in properties) { | |
| if (!accessors.hasOwnProperty(name)) { | |
| buffer.push("\tPublic [" + name + "]") | |
| } | |
| } | |
| $$skipArray.forEach(function (name) { | |
| if (!accessors.hasOwnProperty(name)) { | |
| buffer.push("\tPublic [" + name + "]") | |
| } | |
| }) | |
| buffer.push("\tPublic [" + 'hasOwnProperty' + "]") | |
| //添加访问器属性 | |
| for (name in accessors) { | |
| buffer.push( | |
| //由于不知对方会传入什么,因此set, let都用上 | |
| "\tPublic Property Let [" + name + "](val" + expose + ")", //setter | |
| "\t\tCall [__proxy__](Me,[__data__], \"" + name + "\", val" + expose + ")", | |
| "\tEnd Property", | |
| "\tPublic Property Set [" + name + "](val" + expose + ")", //setter | |
| "\t\tCall [__proxy__](Me,[__data__], \"" + name + "\", val" + expose + ")", | |
| "\tEnd Property", | |
| "\tPublic Property Get [" + name + "]", //getter | |
| "\tOn Error Resume Next", //必须优先使用set语句,否则它会误将数组当字符串返回 | |
| "\t\tSet[" + name + "] = [__proxy__](Me,[__data__],\"" + name + "\")", | |
| "\tIf Err.Number <> 0 Then", | |
| "\t\t[" + name + "] = [__proxy__](Me,[__data__],\"" + name + "\")", | |
| "\tEnd If", | |
| "\tOn Error Goto 0", | |
| "\tEnd Property") | |
| } | |
| buffer.push("End Class") | |
| var code = buffer.join("\r\n"), | |
| realClassName = window['findOrDefineVBClass'](className, code) //如果该VB类已定义，返回类名。否则用className创建一个新类。 | |
| if (realClassName === className) { | |
| window.parseVB([ | |
| "Function " + className + "Factory(a, b)", //创建实例并传入两个关键的参数 | |
| "\tDim o", | |
| "\tSet o = (New " + className + ")(a, b)", | |
| "\tSet " + className + "Factory = o", | |
| "End Function" | |
| ].join("\r\n")) | |
| } | |
| var ret = window[realClassName + "Factory"](accessors, VBMediator) //得到其产品 | |
| return ret //得到其产品 | |
| } | |
| } | |
| } | |
| </script> | |
| </body> | |
| </html> |
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