Angular Interview Questions and Answers

Angular calls lifecycle hooks in a defined order. The constructor runs first and should only inject dependencies. Then ngOnChanges fires whenever a bound input changes, before ngOnInit, which runs once after the first ngOnChanges. After that comes ngOnDestroy. In between, ngOnDestroy comes after view checks: specifically ngOnInit, then ngDoCheck on every change-detection run, followed by ngAfterContentInit and ngAfterContentChecked for projected content, then ngAfterViewInit and ngAfterViewChecked for the component's own view. ngOnDestroy runs once just before the component is removed and is where you unsubscribe, clear timers and detach listeners.

Order matters: ViewChild results are only available in ngAfterViewInit unless the query is static: true. Child views are initialised before the parent's ngAfterViewInit, so the parent hook runs last. Implement the typed interfaces such as OnInit for safety and clarity.

Angular has several binding forms. Interpolation {{ value }} renders a component property into text. Property binding [property]="expr" sets a DOM property or directive input. Attribute binding [attr.aria-label]="expr" sets an attribute when no matching property exists.

Event binding (click)="handler($event)" listens for events, and two-way binding [(ngModel)]="name" combines a value input with a valueChange output; it is sugar for [value]="name" (valueChange)="name = $event".

Class and style bindings use [class.active], [ngClass], [style.width.px] and [ngStyle]. Template reference variables such as #input let you read an element locally, and the $event variable exposes the event payload.

Data flows down through inputs and up through outputs, which is the core mental model. Inputs should be treated as read-only in the child, and the parent owns the state.