原生javascript实现ajax 发送post请求

var postData = {    "name1": "value1",    "name2": "value2"}; postData = (function(obj){ // 转成post需要的字符串.    var str = "";     for(var prop in obj){        str += prop + "=" + obj[prop] + "&"    }    return str;})(postData); var xhr = new XMLHttpRequest(); xhr.open("POST", "../module", true);xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");xhr.onreadystatechange = function(){    var XMLHttpReq = xhr;    if (XMLHttpReq.readyState == 4) {        if (XMLHttpReq.status == 200) {            var text = XMLHttpReq.responseText;             console.log(text);        }    }};xhr.send(postData);