function fetch(url){
return new Promise((res,rej)=>{
let xhr=new XMLHttpRequest();
xhr.open('GET',url);
xhr.onreadystatechange=function(){
if(xhr.readyState==4&&xhr.status==200){
res(xhr.responseText)
}else{
rej(xhr)
}
}
xhr.send()
})
}
fetch(url).then((val)=>{},(err)=>{})
.catch((err)=>{console.log(err)})
