Q.Promise is an alternative promise-creation API that has the same power as the deferred concept, but without introducing another conceptual entity.
Let's rewrite the preceding requestOkText example using Q.Promise:
function requestOkText(url) {
return Q.Promise(function(resolve, reject, notify) {
var request = new XMLHttpRequest();
request.open("GET", url, true);
request.onload = onload;
request.onerror = onerror;
request.onprogress = onprogress;
request.send();
function onload() {
if (request.status === 200) {
resolve(request.responseText);
} else {
reject(new Error("Status code was " + request.status));
}
}
function onerror() {
reject(new Error("Can't XHR " + JSON.stringify(url)));
}
function onprogress(event) {
notify(event.loaded / event.total);
}
...