Top 5 Angular Interview Questions

1. Advantages/disadvantages of Angular
2. Change Detection in Angular
3. Dependency Injection in Angular
4. RxJS library
5. App Performance Optimization

Advantages/disadvantages of Angular

• Advantages: TypeScript, Powerful CLI, Dependency Injection, All-in solution
• Disadvantages: Complexity, Bundle Size, smaller Community

Change Detection

• When to re-render view when data changes
• Traversal dom tree to detect change => expensive
• Use OnPush to optimize: only run change detection when Inputs change or from DOM Events

Dependency Injection

• A Design Pattern implemented by Angular
• Detail implementation is delegated to other classes
• 2 types of injector: Module injector and Component injector
• Resolve injector: look upside from Component to Parent injector
• Resolution modifier: @Optional, @Self, @SkipSelf, @Host

RxJS

• Library to implement Reactive Programming
• Observable vs Promise
• Operators: switchMap, flatMap, concatMap, exhaustMap…
• Subjects: Subject, BehaviorSubject, ReplaySubject…
• Memory leak: unsubscribe, async pipe

Performance Optimization

• Build optimization: AoT
• Lazy loading, differentiate loading
• Treeshakeable
• Runtime optimization: OnPush, trackBy, avoid function call in template => pure pipe, image optimization (src set), CDN…

Bonus Questions

• How do you update your knowledges in Angular