ajax请求封装

var xmlHttp;
    var ajaxRequest = function (params) {
        xmlHttp ={};
        this.url = params.url;
        this.method = params.method;
        this.dataType = params.dataType;
        this.formData = params.formData;//string 仅用于post

        this.init = function(){
            if (window.XMLHttpRequest)
            {
                //  IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
                xmlHttp=new XMLHttpRequest();

            }
            else
            {
                // IE6, IE5 浏览器执行代码
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
            }

            xmlHttp.onreadystatechange = function()
            {
                //这里总是无法调用this.xmlHttp 干脆改成全局变量了
                if (xmlHttp.readyState== && xmlHttp.status==)
                {

                    document.getElementById("myDiv").innerHTML=xmlHttp.responseText;
                }
            }
            xmlHttp.open(this.method, this.url, true);
            xmlHttp.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
            //xmlHttp.setRequestHeader('Content-length', this.formData.length);
            //xmlHttp.setRequestHeader("Referer", "http://www.baidu.com");
            //xmlHttp.setRequestHeader('Connection', 'close');

            return true;

        };

        this.send = function(){
            if(this.init()){
                console.log(this.formData);
                xmlHttp.send(this.formData);
            }
        };

    };
    var FormData = function(){
        this.data = '' ;
        this.append = function(key,val){
            if(typeof key == 'string' && typeof val == 'string')
                this.data += key + '=' + val;
        }
        this.batchAppend = function(a){
            if(typeof a == 'array' || typeof a == 'object')
            {
                for(var i in a)
                {
                    if(typeof a[i] == 'string')
                    {
                        this.data += i + '=' + a[i] + '&';
                    }

                }
                this.data = this.data.substr(,this.data.length-);
            }
        }

        return this.data;

    }
    var data = new FormData();
    data.append('user', 'sachin');
    //data.batchAppend({'fdf':'1313','8':'5454'});
    var params = {
        url : 'http://localhost/test/test.php?b=234234',
        method : 'GET',
        dataType: 'text',
        formData : data
    };
    //console.log(data);
    var request = new ajaxRequest(params);
    request.send();