Top 10 Angular Interview Questions

Overview

This guide provides a structured approach to understanding common Angular interview questions. It aims to equip candidates with the knowledge and insights necessary to effectively demonstrate their expertise in Angular development. The questions cover core concepts, architectural patterns, and practical application of the framework.

Interview Rounds

The interview questions are designed to assess a candidate's understanding across various aspects of Angular.

Question 1: What is Angular, and how is it different from AngularJS?

• Objective: Evaluates the candidate's understanding of the evolution of Angular and its key differences from its predecessor, AngularJS.
• Expected Answer Insight: Angular is a TypeScript-based, component-based framework and a complete rewrite of AngularJS (a JavaScript-based MVC framework). Key differences include improved performance, modularity, and dependency injection. Emphasis should be placed on the shift to reactive programming using RxJS.

Question 2: Explain Angular's architecture.

• Objective: Assesses the candidate's knowledge of the fundamental building blocks of an Angular application.
• Expected Answer Insight: Angular architecture is built upon modules (NgModule), components, templates, services, and directives. Modules group components into functional blocks. Components define the view and interact with services for logic.

Question 3: What is the difference between ngOnInit() and a constructor?

• Objective: Determines the candidate's understanding of Angular lifecycle hooks.
• Expected Answer Insight: The constructor is a TypeScript feature for dependency injection and initialization. ngOnInit() is an Angular lifecycle hook called after Angular initializes the component's data-bound properties.

Question 4: How does data binding work in Angular?

• Objective: Gauges the candidate's familiarity with data binding techniques in Angular.
• Expected Answer Insight: Angular supports four types of data binding: Interpolation (one-way: component to template), Property Binding (one-way: DOM properties), Event Binding (handling events), and Two-Way Binding ([(ngModel)]: data sync between template and component).

Question 5: What is the purpose of RxJS in Angular?

• Objective: Tests the candidate's comfort level with reactive programming in Angular.
• Expected Answer Insight: RxJS (Reactive Extensions for JavaScript) is used for working with asynchronous data streams. It's heavily used with services like HttpClient to manage data responses, create reactive forms, and handle complex event handling with observables.

Question 6: What are directives in Angular, and how are they classified?

• Objective: Evaluates the candidate's knowledge of directives and their role in customizing Angular applications.
• Expected Answer Insight: Directives add behavior to elements in Angular applications. They are classified into three types: Components (directives with a template), Structural Directives (change the DOM layout, e.g., *ngIf, *ngFor), and Attribute Directives (modify the appearance or behavior of an element, e.g., ngClass, ngStyle).

Question 7: How does Angular handle dependency injection (DI)?

• Objective: Assesses the candidate's understanding of dependency injection and its benefits.
• Expected Answer Insight: Dependency injection is a design pattern in Angular that facilitates creating services and injecting them into components or other services. Angular's DI container ensures that instances are shared, preventing memory leaks and maintaining application scalability. DI also supports testing by mocking dependencies.

Question 8: Can you explain the Angular router and how navigation works?

• Objective: Determines the candidate's ability to navigate between views in a Single Page Application (SPA).
• Expected Answer Insight: The Angular Router module enables navigation between views or components. It's configured using RouterModule. The concept of lazy loading optimizes application performance by loading routes as needed.

Question 9: What are Angular Forms, and what is the difference between Template-Driven and Reactive Forms?

• Objective: Evaluates the candidate's knowledge of handling user input in Angular.
• Expected Answer Insight: Angular provides Template-Driven Forms (simpler, rely on directives, best for basic forms) and Reactive Forms (more robust, allowing more control and validation logic, used for complex forms, offering better scalability and testability).

Question 10: What are Angular modules, and why are they important?

• Objective: Tests the candidate's understanding of Angular's modular structure.
• Expected Answer Insight: Modules, defined with @NgModule, group components, services, and other code into functional blocks. They enable code splitting, organization, and lazy loading, which is crucial for large applications. Feature modules enhance modularity and make code more maintainable.

Key Takeaways

A strong understanding of Angular's fundamentals, architecture, and reactive programming principles is essential for success in Angular interviews. Hands-on experience and practical application of these concepts are highly valued. Focus on building small projects and experimenting with code to solidify understanding.