function ajax({url='',type='get',dataType:'json'}){
return new Promise((resolve,reject)=>{
let xhr = new XMLHttpRequest();
xhr.open(type,url,true);
xhr.responseType = dataType;
xhr.onload = function(){
resolve(xhr,response)
}
xhr.onerror = function(err){
reject(err)
}
xhr.send();
})
}
ajax({url:'./a.json'}).then(function(data){console.log(data)},function(data){console.log(data0)})
