仿jquery里的最基本的ajax功能
这个只是最基本的，防止我们总是写无效的代码
代码如下：
function getAjaxRequest() {var request = false;try {request = new XMLHttpRequest();} catch (IE) {try {request = new ActiveXObject("Msxml2.XMLHTTP");} catch (othermicrosoft) {try {request = new ActiveXObject("Microsoft.XMLHTTP");} catch (failed) {request = false;}}}return request;}/** * 构建建议的ajax参数 * options{url:"",data,dataType,callback * @param options */function Ajax(options){var request = getAjaxRequest();var url = options.url;var data = null || options.data;var dataType = (options.dataType || 'GET').toLocaleUpperCase() == 'POST'?'POST':'GET';var callback = options.callback;//回调函数var facade = function(callback){if (request.readyState == 4) {if (request.status == 200) {var responseText = request.responseText;callback && callback(responseText);}}};try{request.open(dataType,url,true);if(dataType == "POST")request.setRequestHeader("Content-Type","application/x-www-form-urlencoded;"); request.onreadystatechange = function(){facade(callback);};request.send(data);}catch(e){throw e;return ;}}