为什么status HTTP状态码会是0?
<body>
<input id="con_" type="text" value=" " >
<button id="submit_">submit</button>
<script>
submit_.onclick = function(){
console.log(1)
var xhr =new XMLHttpRequest();
xhr.open('get','datas.js',true);
xhr.send();
xhr.onload = function(){
console.log(2)
if( xhr.readyState == 4 && xhr.status === 0 ){
console.log(3)
// console.log(xhr.response);
}
}
}
</script>
</body>