原生ajax封装，数据初始化，

var ajaxTool = {
setting : {
method : 'get',
url : location.href,
data : '',
callback : function(){alert('兄弟，你忘记写回掉函数了吧')}
},
ajax :function(json){
//初始化数据
var This = this
this.extend(this.setting,json);//创建一个xhr对象
var   xhr = new XMLHttpRequest();//格式化数据格式 以字符串键值队的形式传递数据
this.setting.data = this.format(this.setting.data);
//发送请求
if(this.setting.method == 'get'){
this.setting.url += "?" + this.setting.data
this.setting.data = null;
}xhr.open(this.setting.method,this.setting.url,true);if(this.setting.method == 'post'){
xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
}//发送请求xhr.send(this.setting.data)//监听请求状态xhr.onreadystatechange = function (){
if(xhr.readyState==4&&xhr.status==200){var result = JSON.stringify(xhr.responseText) //假设请求的是json文件  result = JSON.parse(result); This.setting.callback(result);}
}},
extend :function(obj1,obj2){
for (var attr in obj2) {
obj1[attr] = obj2[attr]
}
},
format : function(data){
var html ="";
for (var attr in data) {
html += attr + '=' + data[attr]+'&';
}html = html.substring(0,html.length-1)
return html;
}}