<!DOCTYPE html>
<html>
<body>
<h2>JavaScript 承诺</h2>
<p id="demo"></p>
<script>
function myDisplayer(some) { document.getElementById("demo").innerHTML = some;}
let myPromise = new Promise(function(myResolve, myReject) { let req = new XMLHttpRequest();
req.open('GET', "mycar.html"); req.onload = function() { if (req.status == 200) { myResolve(req.response);
}
else { myReject("文件未找到"); }
};
req.send();
});
myPromise.then(
function(response) {myDisplayer(response);}, function(error) {myDisplayer(error);});
</script>
</body>
</html>