AngularJS Essentials

Chapter 4
if (result.length > 0) {
successCallback(result);
} else {
errorCallback("No results were found!");
}
}, 1000);
};
var _matches = function (car, criteria) {
return angular.toJson(car).indexOf(criteria) > 0;
};
return {
filter: _filter
}
});
In order to call the filter function properly, we need to pass both callbacks to
perform the success, as follows:
controllers.js
$scope.searchCarsByCriteria = function (criteria) {
carSearchService.filter($scope.cars, criteria, function (result) {
$scope.searchResult = result;
}, function (message) {
$scope.message = message;
});
};
However, there are situations in which the numerous number of callbacks,
sometimes even dangerously chained, may increase the code complexity and
transform the asynchronous algorithms into a source of headaches.
To figure it out, there is an alternative to the massive use of callbacks—the promise
and the deferred patterns. They were created a long time ago and are intended to
support this kind of situation by returning a promise object, which is unknown while
the asynchronous block is processed. As soon as something happens, the promise is
deferred and notifies its handlers. It is created without any side effects and returns
the promise.
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