just-boris just-boris - 1 year ago 78
AngularJS Question

Angularjs promise rejection chaining

I need to create chained promises:

var deferred = $q.defer();
$timeout(function() {
deferred.reject({result: 'errror'});
}, 3000);
deferred.promise.then(angular.noop, function errorHandler(result) {
//some actions
return result;
}).then(function successCallback(result) {
console.log('what do I do here?');
return result;
}, function errorCallback(result) {
$scope.result= result;
return result;

If I put an errorCallback into the first
, the second
will be resolved and its successCallback will be called . But if I remove
then second promise will be rejected.

According to Angular JS docs the only way to propagate rejection is to return
and it looks not obvious, especially because I have to inject
service even if it is not needed;

It can also be done by throwing an exception in
, but it writes exception trace to console, it is not good.

Is there another option to do this in a clear way? And what is the reason? Why it is done? In which case, the current behavior can be useful?

ant ant
Answer Source

And what the reason why it is done. In which case, the current behavior can be useful?

It can be useful when in errorHandler you could try to repair error state and resolve promise somehow.

var retriesCount = 0;

function doWork()
    return $http.post('url')
            // check success-property of returned data
                // just unwrap data from response, may be do some other manipulations
                return response.data;
                // reject with error
                return $q.reject('some error occured');
        .then(/*skip success handler >> */null, function(reason){
            if(retriesCount++ < 3)
                // some error, let me try to recover myself once again
                return doWork();
                // mission failed... finally reject
                return $q.reject(reason);

doWork().then(console.log, console.error);
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