Ajax 跨域问题的解决方案

注：本文转自http://pkzhuclover.iteye.com/admin/blogs/836772

作者未对原理进行太多的说明，需要的时候自己要去读代码，我使用后会把原理补充上。

(function(){
	var id = 1,
		queueList = {};
	
	function apply(o,c){
		if(o){
			for(var k in c){
				o[k] = c[k];
			}
		}
		return o;
	}
	
	/**
	*使用方式
	*scriptRequest({
	*	url:"http://xxx.xxx.xxx",
	*	callback:function(me,data){
	*		//具体操作方法,data为服务器返回数据.
	*	}
	*})
	*/
	function ScriptRequest(config){
		var me = this;
		apply(me,config);
		me.cb = "ScriptRequestCallback_" + id;
		me.scriptID = "ScriptRequestID_" + (id++);
		me.head = document.getElementsByTagName("head")[0];
		me.request();
	}
	
	apply(ScriptRequest.prototype,{
		/**
		*请求地址.
		*/
		//url:""
		/**
		*回调作用域.
		*/
		//scope:null,
		/**
		*@cfg {String}:队列ID,相同的队列ID一次请求未完成时再次请求会自动取消同队列中的上次请求.
		*/
		//queue:null,
		/**
		*@cfg {Number}:超时时间,一次请求的最大请求时间.
		*/
		timeout:30000,
		/**
		*@cfg {Boolean}:自动取消,在有队列的情况下是否自动取消上次请求.
		*/
		autoCancel:true,
		/**
		*@cfg getter {Boolean}:是否处于请求状态.
		*/
		loading:false,
		/**
		*@cfg {String}:后台接收回调方法名的参数名称.
		*以java为例如:
		*String callback = request.getParameter("callback");
		*out.println(callback + "("+ "'输出一串字符串'" +")").
		*/
		callbackName:"callback",
		
		initUrl:function(){
			var me = this,
				code = "?";
			if(me.url.indexOf("?") != -1){
				code = "&";
			}
			me.url += code + me.callbackName + "=" +me.cb;
		},
		
		request:function(){
			var me = this;
			me.transactQueue();
			me.initUrl();
			me.bindListeners();
			var script = document.createElement("script");
			script.setAttribute("src", me.url);
			script.setAttribute("type", "text/javascript");
			script.setAttribute("id", this.scriptID);
			me.script = script;
			me.head.appendChild(script);
			me.loading = true;
		},
		
		bindListeners:function(){
			var me = this;
			window[me.cb] = function(data){
				me.release();
				me.callback && me.callback.call(me.scope || me,me,data);
			}
			me.timeoutThread = setTimeout(function(){
				me.cancel();
			},this.timeout);	
		},
		
		transactQueue:function(){
			var me = this,
				queue=me.queue;
			if(queue){
				var request = queueList[queue];
				request && me.autoCancel && request.cancel();
				queueList[queue] = me;
			}
		},
		
		cancel:function(){
			this.release();	
		},
		
		release:function(){
			var me = this;
			if(me.loading){
				me.loading = false;
				clearTimeout(me.timeoutThread);
				window[me.cb] = undefined;
				try{
					delete window[me.cb];
				}catch(e){}
				me.script && me.head.removeChild(me.script);
			}
		}
	});
	
	this.scriptRequest = function(config){
		return new ScriptRequest(config);
	};
})();