js实现面向切面的编程（AOP）
Email:longsu2010 at yeah dot net
面向切面的编程（AOP）还是有点意思的，可以在不修改原有代码的情况下增加新功能。有一些js框架实现AOP功能，但是有些时候我们并不能依赖于框架写程序（框架可能很笨重），我们需要自己实现一些适合我们的功能模块。下面是我自己实现的js AOP，实现了before和after功能，仅供抛砖。
如下是aspect.js，是实现AOP的全过程。
(function(window, undefined){function aspect(type){return function(target, methodName, advice){var exist = target[methodName],dispatcher;if( !exist || exist.target != target ){dispatcher = target[methodName] = function(){// before methodsvar beforeArr = dispatcher.before;var args = arguments;for(var l = beforeArr.length ; l--; ){args = beforeArr[l].advice.apply(this, args) || args;}// target methodvar rs = dispatcher.method.apply(this, args);// after methodsvar afterArr = dispatcher.after;for(var i = 0, ii = afterArr.length; i < ii; i++){rs = afterArr[i].advice.call(this, rs, args) || rs;}// return objectreturn rs;}dispatcher.before = [];dispatcher.after = [];if( exist ){dispatcher.method = exist;}dispatcher.target = target;}var aspectArr = (dispatcher || exist)[type];var obj = {advice : advice,_index : aspectArr.length,remove : function(){aspectArr.splice(this._index, 1);}};aspectArr.push(obj);return obj;};}window.aspect = {before : aspect("before"),after : aspect("after")};return window.aspect; })(window, undefined);以下是测试代码：
var as = window.aspect;var obj = {url:"",get : function(key){return this["key"];},set : function(key, value){this["key"] = value;} };var h1 = as.before(obj, "set", function(key, value){// 返回一个数组可以修改参数value += " before-1 ";//console.log(value);return [key, value]; });var h2 = as.before(obj, "set", function(key, value){// 没有返回值则参数不会变化value += " before-2 ";//console.log(value); });obj.set("url", "http://mojijs.com");console.log( obj.get("url") );var h3 = as.after(obj, "get", function(value){// 没有返回值不会修改原函数的返回值value += " after-1 ";//console.log(value);});var h4 = as.after(obj, "get", function(value){// 有返回值会修改原函数的返回值value += " after-2 ";//console.log(value);return value;});console.log( obj.get("url") );h1.remove(); // 删除切面方法h4.remove(); // 删除切面方法obj.set("url", "http://baidu.com");console.log( obj.get("url") );