Creating promise wrappers with $q.when()

AngularJS includes the $q.when() method that allows you to normalize JavaScript objects into promise objects.

How to do it…

The $q.when() method accepts promise and non-promise objects, as follows:

var deferred = $q.defer()
  , promise = deferred.promise;

$q.when(123);
$q.when(promise);
// both create new promise objects

If $q.when() is passed a non-promise object, it is effectively the same as creating an immediately resolved promise object, as shown here:

var newPromise = $q.when(123);

// promise will wait for a $digest cycle to update $$state.status,
// this forces it to update for inspection
$scope.$apply();

// inspecting the status reveals it has already resolved
$log.log(newPromise.$$state.status);
// 1

// since it is resolved, the handler will execute immediately
newPromise.then($log.log);
// 123

Tip

JSFiddle: http://jsfiddle.net/msfrisbie/ftgydnqn/

How it works…

The $q.when() method wraps whatever is passed to it with a new promise. If it is passed...