ajax封装

function ajax(method,url,json,success,error){
var xml = new XMLHttpRequest()|| new ActiveXObject("Microsoft,XMLHTTP");
var str = '';
for(var key in json){
str+="&"+key+"="+json[key];
}
str = str.substr(1);
if(method == "get"){
url = url+"?"+str;
xml.open("get",url,true);
xml.send();
}else{
xml.open("post",url,true);
xml.setRequestHeader("content-type","application/x-www-form-urlencoded");
xml.send(str);
}

xml.onreadystatechange = function(){
if(xml.readyState == 4 && xml.status == 200){
var data = xml.responseText;

if(typeof data !="object"){
data = JSON.parse(data);
}
success&&success(data);
}else{
error&&error(xml.status);
}
}
}