Angular

ReTry & ReTryWhen Angular Tutorial Subjects in Angular   In this tutorial let us learn how to Unsubscribe from an observable in angular. An observable which is not Unsubscribed will lead to memory leak & Performance degradation. Why Unsubscribe In the example below, we have ChildComponent, which subscribes to an observable in its ngOnInit hook. […]

The take, takeUntil, takeWhile & takeLast operators allow us to filter out the emitted values from the observable. The take(n) emits the first n values, while takeLast(n) emits the last n values. The takeUntil(notifier) keeps emitting the values until it is notified to stop. takeWhile(predicate) emits the value while values satisfy the predicate. All of the stops emitting once done.

Angular ThrowError operator returns an observable, which on subscription immediately errors out. It does not emit any results.

NgModelChange is an Angular specific event, which we can use to listen for changes to the user input. It is the @Output property of the ngModel directive, Hence we need to use it along with it. ngModle raises the NgModelChange event, whenever the model changes. Another way to listen for change is to use the change DOM event. We also learn how to use them and also the difference between change & ngModelChange.

The expression has changed after it was checked (Expressionchangedafterithasbeencheckederror) is one of the common errors, that we encounter in Angular applications. The error arises when the binding expression changes after angular checked it during the change detection cycle.