Promises
in Angular JS
What is a Promise?
A promise represents the result of
an asynchronous operation
AN async Experience
JS Async Operations
setTimeout/setInterval
XmlHttpRequest (AJAX)
Web Workers
Element Creation/OnLoad
Generators
Promise Facts
- A Promise represents a task that will finish in the future
- A Promise is a representation of an asynchronous activity
-
A Promise is an instance with three methods
-
then()
- catch()
- finally()
- A Promise will eventually be resolved or rejected
A promise is in one of three different states
* Immutable
AngularJS Deferred API
Implemented using the $q service
Typical Use Case
function myPromise() {
var deferred = $q.defer();
doSomethingAsync( function( result ) {
deferred.resolve( result );
} );
return deferred.promise;
}
AngularJS Promise API
Result of
deferred.promise
var p = myPromise();
p.then( success, error, notify )
p.catch( error )
p.finally ( callback )
Code Examples
GitHub: github.com/Transcordia/ng-meetup
Promises
By James Cook
