promise_ajax封装

function creatXHR(){
if(window.XMLHttpRequest){
return new XMLHttpRequest();
}
return new ActiveXObject("Msxml2.XMLHTTP");
}


function parmes(obj){
var str="";
for(var key in obj){
str+=key+"="+obj[key]+"&";
}
return str;
}




function ajax(json){
var xhr=new creatXHR();
var p=new Promise(function(resolve,reject){

if(json.type=="get"){
xhr.open("get",json.url+"?"+parmes(json.data),json.async);
xhr.send(null)
}else{
xhr.open("post",json.url,json.async);
xhr.setRequestHeader("Cotent-Type","application/x-www-form-urlencoded");
xhr.send(parmes(json.data))
}


if(json.async==true){
xhr.onreadystatechange=function(){
if(xhr.readyState==4){
callback(xhr,json,resolve,reject)
}
}
}else{
callback(xhr,json,resolve,reject)
}


});
return p;
}


function callback(xhr,json,resolve,reject){
if(xhr.status==200){
if(json.success){
json.success(result)
}
resolve(xhr.responseText);
}else{
reject({"errorcode":xhr.status,"msg":xhr.statusText})
}
}