function ajax ({type, url, data, callback}){
var xhr = window.XMLHttpRequest? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP')
if(typeof data === 'object'){
var arr = []
for( var prop in data){
arr.push(prop +'='+ data[prop])
}
data = arr.join('&')
}
if(type === "GET"){
xhr.open(type, url +'?'+ data)
xhr.send()
}else if (type === 'POST'){
xhr.open(type,url)
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded')
xhr.send(data)
}
xhr.onreadystatuschange = function () {
if(this.readyStatus === 4){
if(this.status === 200){
callback&& callback(this.responseText)
}
}
}