纯JS封装Ajax对象

封装好的对象：

var Ajax = function (sUrl, sMethod, oParam, fCallback) {
    this.sUrl = sUrl;
    this.sMethod = sMethod;
    this.oParam = oParam;
    this.fCallback = fCallback;
    this.status = {
        1: '请求成功',
        2: 'http返回失败',
        3: '数据加载中'
    }
    this.xmlHttp = null;
    //驱动函数  
    this.Driver = function () {
        this.xmlHttp = this.CreateXmlHttp();
        this.xmlHttp.open(this.sMethod, this.sUrl, true);
        this.xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        this.xmlHttp.onreadystatechange = GetResult; //指定回调函数   
        this.xmlHttp.send(this.oParam); //发送请求   
    };
    //创建操作对象  
    this.CreateXmlHttp = function () {
        var xmlHttp;
        if (window.ActiveXObject) { //IE下   
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        if (window.XMLHttpRequest) { //其他浏览器如火狐   
            xmlHttp = new XMLHttpRequest();
        }
        return xmlHttp;
    };
    //回调方法  
    var GetResult = function () {
        if (this.readyState == 4) {//请求状态为4表示成功    
            if (this.status == 200) {//http状态200表示OK    
                eval(fCallback)(this.responseText);
            } else {//http返回状态失败    
                return this.status[2];
            }
        } else {//请求状态还没有成功，页面等待    
            return this.status[3];
        }
    }
}

调用方法：

new Ajax('test.php', 'get', {}, function (responseText) {
    alert(responseText);
}).Driver();