Angular 8 Interview Questions and Answers for 7 years experience

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Angular 8 Interview Questions and Answers

  1. What are the key differences between AngularJS and Angular (Angular 8)?

    • Answer: AngularJS (Angular 1.x) is a JavaScript MVC framework, while Angular (2+) is a TypeScript-based component-based framework. Key differences include: architecture (MVC vs. component-based), programming language (JavaScript vs. TypeScript), dependency injection, mobile support (better in Angular), and performance (Angular is generally faster).

  2. Explain Angular's component lifecycle hooks.

    • Answer: Angular components have lifecycle hooks that allow you to execute code at specific points in a component's life. These include `ngOnChanges`, `ngOnInit`, `ngDoCheck`, `ngAfterContentInit`, `ngAfterContentChecked`, `ngAfterViewInit`, `ngAfterViewChecked`, and `ngOnDestroy`. Each hook serves a distinct purpose, enabling tasks like initializing data, detecting changes, and cleaning up resources before component destruction.

  3. What is Angular's dependency injection system? How does it work?

    • Answer: Angular's dependency injection system is a powerful mechanism for providing dependencies to components and services. It manages the creation and provision of dependencies, making code more modular, testable, and maintainable. It works by defining dependencies in a component's constructor and letting the injector provide those dependencies based on configured providers.

  4. Explain the difference between `async` and `await` in Angular.

    • Answer: `async` and `await` are keywords used to simplify asynchronous code. `async` declares an asynchronous function that returns a Promise. `await` can only be used inside an `async` function; it pauses execution until the Promise it's awaiting resolves, making asynchronous code look and behave a bit more like synchronous code.

  5. How do you handle HTTP requests in Angular?

    • Answer: Angular's `HttpClient` module is used to make HTTP requests. It's easy to use and provides methods for GET, POST, PUT, DELETE, etc. It handles error handling and response transformation efficiently. Typically, you inject `HttpClient` into your service and use its methods to interact with an API.

  6. Describe different routing strategies in Angular.

    • Answer: Angular uses the `RouterModule` for routing. Common strategies include using `forRoot()` to create a root router module and `forChild()` for lazy-loaded modules. Different routing strategies help optimize the application by loading only necessary modules when needed, improving performance.

  7. Explain Angular's change detection mechanism.

    • Answer: Angular uses a change detection mechanism to update the view when the underlying data changes. By default, it uses a zone-based approach, detecting changes automatically within the Angular zone. More advanced strategies like `OnPush` change detection can be used to optimize performance by only checking for changes when specific conditions are met.

  8. What are RxJS Observables and how are they used in Angular?

    • Answer: RxJS Observables are used to handle asynchronous data streams. They provide powerful operators for manipulating and transforming data streams, making them ideal for handling events, HTTP requests, and other asynchronous operations. In Angular, they're often used with `HttpClient` to manage HTTP responses.

  9. How do you implement forms in Angular?

    • Answer: Angular offers two approaches: template-driven forms and reactive forms. Template-driven forms utilize directives like `ngModel` for simpler forms, while reactive forms, using `FormGroup`, `FormControl`, etc., provide more control and are better suited for complex forms with validation logic.

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