(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 methods

					var beforeArr = dispatcher.before;

					var args = arguments;

					for(var l = beforeArr.length ; l--; ){

						args = beforeArr[l].advice.apply(this, args) || args;

					}

					// target method

					var rs = dispatcher.method.apply(this, args);

					// after methods

					var afterArr = dispatcher.after;

					for(var i = 0, ii = afterArr.length; i < ii; i++){

						rs = afterArr[i].advice.call(this, rs, args) || rs;

					}

					// return object

					return 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);

// 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") );