Angular Interview Questions: Top 10 Questions with Answers- April 2020

Angular 9 Interview Questions

Due to the fact that Angular is such a popular framework, you’ll be frequently asked about it in developer interviews. So if you wish to get a development job and are going to fight an interview for the same, its time you refine your knowledge about Angular. Here are 10 Angular interview questions that are asked in interviews very often. Most of these Angular interview questions are valid for Angular version 5 and up.

  1. What is Angular?
  2. Why do developers use Angular?
  3. What is the difference between Angular and AngularJS?
  4. Name some features of Angular
  5. What Are Differences in Angular 9 and Angular 8?
  6. What is Ivy? What is its purpose?
  7. Explain AOT and JIT compilations
  8. What are some key differences between AOT and JIT compilation processes?
  9. Explain the Unit testing setup in Angular 9?
  10. What is Angular Universal?

If you’re new to Angular, you might be interested in understanding the Angular Project Structure. If you’re just interested in Angular overall, take a look at our other Angular Related Articles.

1. What is Angular?

Angular is one of the most well known open source frameworks for developing Single Page Applications (SPAs). It is written and backed by the Angular team at Google. It was originally written in Javascript as AngularJS which was eventually rewritten in Typescript. Angular is hugely popular among the Developers community. We can use Angular for developing Web Applications as well as Mobile Applications (by using frameworks like Ionic).  It integrates powerful features like declarative templates, an end to end tooling, dependency injection and various other best practices that smoothens the development path.

2. Why do developers use Angular?

Using Angular for application or website development comes with certain advantages. It provides a wide array of tools and functionalities to build scalable web applications, fast and efficiently. With backing from Google, it is a reliable framework for web development. Further advantages that make people use Angular are as follows-

  • The opinionated development approach helps manage enterprise level codebases.
  • Angular provides a toolset to make developers’ life easy by simplifying things like linting, unit testing, integration testing, and build process
  • Angular allows creating Web Components (Angular Elements) which can be used outside Angular apps
  • Angular release a new major version every 6-8 months
  • Angular uses Typescript which allows developers to use the latest ECMA script features without worrying about browser support.
  • The huge Angular developer community means you’d always get support if you hit roadblocks while developing apps.
  • Angular works on MVC patten architecture and supports two-way binding.
  • Angular supports both Angular and static templates.
  • Angular supports Restful API and enables developers to create custom directives.
  • Angular provides many features like animation.
  • It supports dependency injections and client and server communication.

3. What is the difference between Angular and AngularJS?

Angular is a completely rewritten component-based framework in which an application is a tree of individual components. Some of the major difference in tabular form

AngularJSAngular
It is based on MVC architectureThis is based on Service/Controller
This uses use JavaScript to build the applicationIntroduced the typescript to write the application
Based on controllers conceptThis is a component-based UI approach
Not a mobile-friendly frameworkDeveloped considering the mobile platform
Difficulty in SEO friendly application developmentEase to create SEO friendly applications

4. Name some features of Angular

  • Efficient Two-way data binding
  • Creating custom Events and Event binding
  • Angular uses Typescript which means developers can always use the latest ECMA script features without worrying about Browser support
  • Angular is Cross-platform
  • Provides development speed and optimum performance
  • Angular Universal allows Server-Side rendering of Angular applications
  • Angular CLI follows the industry best-practices and provides several features to help ease the development processes and let developers focus on business logic
  • Dependency Injection provides an easy and clean way to make dependencies available when needed

5. What Are Differences in Angular 9 and Angular 8?

At the time of writing this article, Angular 9 is the latest version of Angular which was released in February 2020. Here are some new features introduced with Angular 9:

  • Brand new Ivy renderer: Ivy was included with Angular 8 but was not enabled by default. With Angular 9, Ivy is the enabled as the default renderer.
  • Added undecorated classes migration schematic in the core.
  • The formControlName also accepts a number in the form
  • Now allow selector-less directives as base classes in View Engine in the compiler.
  • Added support selector-less directive as base classes in Ivy and also make the Ivy compiler the default for ngc.
  • Convert all ngtsc diagnostics to ts.Diagnostics
  • bazel: support ts_library targets as entry-points for ng_package.
  • core: add dynamic queries schematic.
  • core: Mark TestBed.get as deprecated.
  • ivy: expose window.ng.getDebugNode helper and also support ng-add in localize package.
  • ivy: i18n – add syntax support for $localize metadata block.
  • ivy: i18n – reorganize entry-points for better reuse.
  • language-service: enable logging on TypeScriptHost.
  • language-service: provide diagnostic for invalid templateUrls.
  • language-service: provide diagnostics for invalid styleUrls.

6. What is Ivy? What is its purpose?

Angular Ivy is a new rendering engine for Angular. You can choose to opt-in a preview version of Ivy from Angular version 8. Angular 9 comes with Ivy enabled as default renderer. Ivy reduced the build time and bundle sizes by a considerable amount. AOT compilation with Ivy is faster and should be used by default.

7. Explain AOT and JIT compilations

Angular applications consist of mainly custom components and their templates. Since browsers cannot understand these Angular-Style Components and their templates, We need to compile Angular applications using the Angular framework (duh!) before they can run in the Browser. The Angular just-in-time (JIT) compilation, as the name suggests loads both the application code and the Angular Compiler in the browser and compiles the code at runtime. This converts the source code to a code that the browser can understand. All this happens before you see the application loaded on the browser screen. As you can guess, the browser has to load a lot of extra code (the Angular Compiler) into the browser to facilitate the compilation which results in more Bytes transferred on the internet and more processing required at runtime. The Angular ahead-of-time (AOT) compilation, on the other hand, converts the HTML and Typescript code into a minified, more efficient JavaScript code during the build process. As a result, you get pre-compiled code bundles that the browser can understand and do not need the Angular Compiler to be loaded separately. AOT generated smaller output bundles which result in the faster rendering of the application in the browser.

8. What are some key differences between AOT and JIT compilation processes?

AOTJIT
Generates browser understandable code during the build processGenerated browser understandable code at runtime 
Bundles generated with AOT do not contain Angular CompilerBundles generated with JIT contain Angular Compiler code
Template binding errors can be detected in the build phaseTemplate binding errors can be viewed at runtime
Provides faster rendering of the applicationRendering of application is comparatively slower than AOT
Bundle sizes are smaller as compared to JITBundle sizes will be bigger because of extra Angular Compiler code
Suitable for Production buildsSuitable for development and testing builds

9. Explain the Unit testing setup in Angular 9?

Angular applications created with Angular CLI come with a built-in, ready-to-use Unit testing setup. Angular CLI downloads and installs everything needed with the Jasmine test framework. All you need to do is run ng test to execute the tests and see the test results. By default, this command builds the app in watch mode and launches the Karma test runner. The output of test results would be shown in Terminal and/or the browser of your choice.

10. What is Angular Universal?

Angular Universal is a server-side rendering module for Angular applications in various scenarios. Using Angular Universal, you can configure your server to return compiled code so it doesn’t need to be done in the browser. Angular Universal was created primarily to solve some Search Engine Optimization (SEO) issues with applications built with Angular. Many of those issues are no longer valid as Search engines since then have improved crawling support for websites using Web Components  This is a community-driven project and available under the @angular/platform-server package.

This is the first of many sets of Angular interview questions. I’ll be back with set 2 very soon. I hope this helps you crack that interview. Good luck!

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