Angular’s route guards are interfaces which can tell the router whether or not it should allow navigation to a requested route. They make this decision by looking for a true or false return value from a class which implements the given guard interface. There are five different types of guards and each of them is […]

Reactive form keeps the data model pure by providing it as an immutable data structure. It uses an immutable approach to manage the state of a form. In other words, it will not mutate the form state. Each time a change occurs to the form, the FormControl instance will not update the existing data model, […]

(change) event bound to classical input change event. You can use (change) events even if you don’t have a model at your input. (ngModelChange) is the @Output of ngModel directive. It fires when the model changes. You cannot use this event without ngModel directive.

This operator is best used when you have a group of observables and only care about the final emitted value of each. One common use case for this is if you wish to issue multiple requests on page load (or some other event) and only want to take action when a response has been received […]

As soon as a promise is made, the execution takes place. However, this is not the case with observables because they are lazy. This means that nothing happens until a subscription is made. While promises handle a single event, observable is a stream that allows passing of more than one event. A callback is made […]