AngularJS also offers the ability to provide notifications about promises before a final state has been reached. This is especially useful when promises have long latencies and updates on their progress is desirable, such as progress bars.
The promise.then() method accepts a third argument, a notification handler, which can be accessed through the deferred an unlimited number of times until the promise state has been resolved. This is shown here:
promise
.then(
// resolved handler
function() {
$log.log('success');
},
// empty rejected handler
null,
// notification handler
$log.log
);
function resolveWithProgressNotifications() {
for (var i=0; i<=100; i+=20) {
// pass the data to the notification handler
deferred.notify(i);
if (i>=100) { deferred.resolve() };
};
}
resolveWithProgressNotifications();
// 0
// 20
// 40
// 60
// 80
// 100
// "success"Tip
JSFiddle: http://jsfiddle.net/msfrisbie/5798q0ru/