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);