简单的 创建AJax的方法

// 简单的ajax对象
var myAjax = {
// XMLHttpRequest IE7+, Firefox, Chrome, Opera, Safari ；  ActiveXObject IE6, IE5
xhr: window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP'),
get: function(url, callback){
this.xhr.open('get', url);
this.onreadystatechange(callback, this.xhr);
this.xhr.send(null);
},
post: function(url, data, callback){
this.xhr.open('post', url);
this.xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
this.onreadystatechange(callback, this.xhr);
this.xhr.send(data);
},
onreadystatechange: function(func, _xhr){
_xhr.onreadystatechange = function(){
if(_xhr.readyState == 4){
if (_xhr.status == 200){
func(_xhr.responseText);
}
}
}
}
};