Why are Callbacks from Promise `.then` Methods an Anti-Pattern

Question

I have seen answers on StackOverflow where people suggest furnishing a callback function to an AngularJS service.

app.controller(\'tokenCtrl\', function($sco         


        

Answer 1

The code can be re-factored as follows:

app.controller('tokenCtrl', function($scope, tokenService) {
    tokenService.getTokens.then ( callbackFn(tokens) {
        $scope.tokens = tokens;
    });
});

app.factory('tokenService', function($http) {
    var getTokens = function() {
        //return promise
        return $http.get('/api/tokens').then (function onFulfilled(response) {
                //return tokens
                return response.data;
            }
        );
    };

    return {
        getTokens: getTokens
    };
});

By having the service return a promise, and using the .then method of the promise, the same functionality is achieved with the following benefits:

• The promise can be saved and used for chaining.

• The promise can be saved and used to avoid repeating the same $http call.

• Error information is retained and can be retrieved with the .catch method.

• The promise can be forwarded to other clients.