Master Angular 8: Essential Interview Questions & Answers

This comprehensive guide prepares you for Angular 8 interviews by covering a wide range of frequently asked questions. We explore core Angular 8 concepts, including its features (differential loading, dynamic imports, web workers, Ivy rendering engine), upgrade processes from previous versions, and reasons for its popularity in modern application development. This resource delves into key architectural components (NgModules, components, templates), directives (`ngFor`, `ngIf`), data binding, and form handling (template-driven vs. reactive forms). We also cover advanced topics like Angular Universal, AOT compilation, Bazel, promises vs. observables, and the use of wildcard routes. This guide provides the knowledge and confidence to excel in your next Angular 8 interview.

Top Angular 8 Interview Questions and Answers

What is Angular 8?

Angular 8 is a client-side framework built using TypeScript, designed for creating dynamic web applications. It's a significant evolution from AngularJS (Angular 1.x), representing a complete rewrite and incorporating many performance improvements and features.

Angular 8 Release and Key Differences from Angular 7

Angular 8 was released on May 28, 2019. Key improvements over Angular 7 include:

  • Differential Loading: Optimized loading of application code based on browser capabilities.
  • Dynamic Imports for Lazy Routes: Improved lazy loading for faster initial app load times.
  • Web Workers Support: Offloads tasks to background threads for enhanced performance.
  • TypeScript 3.4 Support: Utilizes the latest TypeScript features.
  • Angular Ivy (Opt-in Preview): A new rendering engine offering improved build times, smaller bundle sizes, better debugging, and backward compatibility.

Upgrading to Angular 8

To upgrade from an older Angular version to Angular 8:

  1. Check your current Angular version: ng --version
  2. Uninstall the older version: npm uninstall -g angular-cli (or sudo npm uninstall -g angular-cli on macOS)
  3. Clear the npm cache: npm cache verify and npm cache clean
  4. Install Angular 8: npm install -g @angular/cli@latest
  5. Verify the installation: ng --version

Reasons for Angular's Popularity

Angular's popularity stems from its combination of declarative templates, dependency injection, powerful tooling, and high performance. It simplifies development and allows for creating web and mobile applications.

Prominent Features of Angular 8

  • Cross-Platform Capabilities: Build Progressive Web Apps (PWAs), native mobile apps (using Ionic, Cordova, or NativeScript), and desktop apps.
  • Improved Speed and Performance: Optimized code generation, faster lazy loading, and SEO-friendly apps.
  • High Productivity: Simplified template syntax, powerful CLI, and good IDE integration.
  • Full Development Support: Built-in animation support, accessibility features, and comprehensive documentation.

Latest Angular Version

As of this writing, the latest released version of Angular is Angular 15.

Key Differences: Angular 7 vs. Angular 8

Angular 7 Angular 8
Larger, potentially more complex to use. Smaller, faster, and easier to use.
Features: Angular Material, CLI prompts, drag-and-drop, virtual scrolling. Features: Ivy rendering engine, Bazel support, differential loading, improved CLI.
Supported by all Node.js versions. Requires Node.js version 12 or later.
Supports an older version of TypeScript. Supports TypeScript 3.4.x

Bazel in Angular 8

Bazel is a build system that offers improved build performance and customization options for Angular projects.

Wildcard Routes in Angular 8

Wildcard routes (using `**`) handle URLs that don't match any other defined routes in the application.

Promises vs. Observables in Angular 8

Promises Observables
Handle single asynchronous events. Handle sequences of asynchronous events over time.
Always asynchronous. Can be synchronous or asynchronous.
Return a single value. Can emit multiple values.
Not cancellable. Cancellable via unsubscribe().
No built-in operators. Support various operators (map, filter, etc.).

Codelyzer

Codelyzer is a static analysis tool for Angular projects that checks adherence to coding standards and best practices using TSLint.

Performance Enhancements in Angular 8

Angular 8's performance improvements result from features like differential loading, improved lazy loading, and the Ivy rendering engine.

Angular Ivy

Ivy is a new rendering engine in Angular that improves build times, bundle sizes, debugging, and template type checking. It was made the default in Angular 9.

Wildcard Routes (Continued)

Wildcard routes are used in Angular's routing to handle any URL that doesn't have an explicit route defined. This is often used for catch-all routes or 404 pages.

What is Angular 8?

Angular 8 is a powerful JavaScript framework built with TypeScript, used for building dynamic and responsive web applications. It builds upon previous versions, offering enhanced features and performance improvements.

Angular 8's Release and Key Features

Released on May 28, 2019, Angular 8 shares similarities with its predecessors but introduces several key enhancements:

  • Differential Loading: Serves optimized code based on the browser's capabilities, resulting in faster load times.
  • Dynamic Imports for Lazy Routes: Improves the speed of lazy-loaded modules.
  • Web Workers: Enables offloading tasks to background threads, improving responsiveness.
  • TypeScript 3.4 Support: Leverages the latest features of TypeScript.
  • Angular Ivy (Opt-in): A new rendering engine providing better performance, smaller bundle sizes, improved debugging, and backward compatibility (became default in Angular 9).

Upgrading to Angular 8

Upgrading your project to Angular 8 is straightforward using the Angular CLI:

  1. Check your current version: ng --version
  2. Uninstall the old CLI: npm uninstall -g @angular/cli (use sudo on macOS)
  3. Clear the npm cache: npm cache verify and npm cache clean --force
  4. Install the latest CLI: npm install -g @angular/cli@latest
  5. Verify the new version: ng --version

Reasons for Angular's Popularity

Angular's popularity is driven by its:

  • Declarative Templates: Easy-to-understand templates for creating user interfaces.
  • Dependency Injection: Promotes modularity and testability.
  • End-to-End Tooling: Comprehensive tools simplify development, testing, and deployment.
  • High Performance: Optimized code and features for creating fast and responsive applications.
  • Cross-Platform Development: Build for web, mobile, and desktop.

Key Features of Angular 8

Angular 8 offers several compelling features, making it a powerful choice for web application development.

  • Cross-Platform Development: Supports PWAs, native mobile apps, and desktop apps.
  • Performance Improvements: Faster load times, optimized code, and SEO-friendly applications.
  • High Productivity: Streamlined development with the CLI, improved tooling, and easy-to-use templates.
  • Robust Ecosystem: A large community, extensive documentation, and many supporting libraries.

Angular 7 vs. Angular 8: Key Differences

Angular 7 Angular 8
Potentially more complex to work with due to platform-wide updates. Smaller, faster, and more streamlined.
Focused on updates to Angular Material, CLI prompts, drag-and-drop, virtual scrolling. Key features include Ivy rendering engine, Bazel support, differential loading.
Supported by all Node.js versions. Requires Node.js 12 or later.
Supported older TypeScript versions. Supports TypeScript 3.4.x

Bazel in Angular 8

Bazel is a fast and reliable build system that can be used with Angular projects. It provides a consistent build process for both front-end and back-end development.

Wildcard Routes in Angular 8

Wildcard routes (using `*` or `**`) act as catch-all routes, handling URLs that don't match any other specified routes in your Angular application's routing configuration. These are usually placed at the end of your route definitions.

Promises vs. Observables

Promises Observables
Handle a single asynchronous operation. Handle multiple asynchronous events over time.
Not cancellable. Cancellable using unsubscribe().
Return a single value. Can emit multiple values.
Execute immediately. Lazy; execute when subscribed to.

Codelyzer

Codelyzer is a tool that helps maintain code quality in Angular projects by checking adherence to coding best practices. It works alongside TSLint (or ESLint in newer Angular versions) to perform static code analysis.

Performance Improvements in Angular 8

Angular 8 boasts significant performance enhancements due to features such as differential loading, improved lazy loading, and the introduction of the Ivy rendering engine.

Angular Ivy

Ivy is a next-generation rendering engine for Angular. It offers improved build times, smaller bundle sizes, better debugging capabilities, and enhanced type checking. It significantly improves the developer experience and application performance.

Checking Angular CLI Version

Use the command ng version to determine your currently installed Angular CLI version.

Running an Angular App

The command ng serve starts a development server, compiling and serving your Angular application. It also provides live reloading.

Installing the Latest Angular CLI

Use this command to install the latest version of the Angular CLI: npm install -g @angular/cli@latest

`typeof` Checks in Angular 8

The typeof operator in Angular 8 (and JavaScript) allows you to check the data type of a variable. This is useful for runtime type validation.

Key Parts of the Angular 8 Architecture

Angular 8 applications are built upon these core architectural components:

  • Modules (NgModules): Organize the application's code into reusable blocks.
  • Components: Manage the UI elements and data.
  • Templates: HTML that defines the user interface.
  • Metadata: Decorators providing information about classes.
  • Data Binding: Connects data to the UI.
  • Directives: Add behavior to the DOM.
  • Services: Provide reusable logic and data access.
  • Dependency Injection: Manages the dependencies between components and services.

Angular 8 Components

Components are the fundamental building blocks. Each component has a class (containing logic and data) and a template (defining the view).

NgModule in Angular 8

NgModules organize the application’s code into cohesive blocks. They manage the compilation context for components and define dependencies.

NgUpgrade in Angular 8

NgUpgrade is a library that helps integrate AngularJS components into an Angular application.

Angular 8 `ngFor` Directive

The *ngFor directive iterates over an array or iterable object to create and render elements for each item in the list. It provides context variables like index, even, and odd.

Angular 8 `ngIf` Directive

The *ngIf directive conditionally renders a template based on a boolean condition. If the condition is true, the element is added to the DOM; if false, it's removed.

Data Binding in Angular 8

Data binding enables communication between a component's data and its template. Angular 8 supports one-way and two-way data binding.

String Interpolation in Angular 8

String interpolation () is a way to display data from your component's TypeScript code within your HTML template (one-way binding).

Event Binding in Angular 8

Event binding allows you to respond to DOM events (clicks, changes, etc.) by calling methods within your component's TypeScript code.

Creating an Angular 8 App

Create a new Angular 8 project using the Angular CLI: ng new my-app-name

Angular 8 Forms

Angular 8 provides two approaches for handling forms:

  • Template-driven forms: Simpler for basic forms using two-way data binding.
  • Reactive forms: More robust and scalable for complex forms using RxJS.

Reactive Forms in Angular 8

Reactive forms use a model-driven approach, providing better control over form state and validation.

Template-Driven Forms in Angular 8

Template-driven forms are simpler to implement but less scalable than reactive forms. They're suitable for less complex forms.

Reactive Forms vs. Template-Driven Forms

Reactive Forms Template-Driven Forms
More robust, scalable, and testable. Uses RxJS. Simpler, suitable for basic forms. Uses two-way data binding.
Better for complex forms and applications using reactive patterns. Suitable for simple forms and less complex applications.

Angular Universal

Angular Universal allows you to render your Angular application on a server, improving SEO and performance.

Angular Universal (Server-Side Rendering)

Angular Universal is a technology that renders Angular applications on the server instead of solely in the browser (client-side rendering, CSR). This server-side rendering (SSR) approach generates static HTML pages that load faster, improving the initial user experience. Users see the basic layout more quickly, even before the full application becomes interactive. This is particularly beneficial for SEO and performance.

AOT (Ahead-of-Time) Compilation in Angular 8

AOT (Ahead-of-Time) compilation compiles Angular components and templates during the build process, rather than at runtime in the browser. This results in faster initial load times because the browser doesn't need to compile the application code before rendering.

AOT offers several performance advantages:

  • Faster initial load times due to pre-compilation.
  • Reduced client-side processing as templates are already compiled.
  • Removal of unused components and directives, leading to smaller bundle sizes.