Angular 2 Interview Questions

Angular 2 Interview Questions | Freshers & Experienced

  • Sharad Jaiswal
  • 25th Nov, 2021

About Angular 2

Angular 2, the longest awaited sequel of AngularJS, used to design dynamic and single web applications. You may be wondered why Angular 2 is launched, as AngularJS was already popular among users. Well, you will get all your answers when you read online interview questions on Angular 2 as well as AngularJS. Here, I give you a brief introduction about why Angular 2 is released. Angular 2 shows better performance than AngularJS in loading mobile applications. Unlike AngularJS, Angular 2 is written in typescript, and architecture is based on a component-based approach. Read the below article to know more about what's new in Angular 2, and its cons and pros. Here, we have the best collection of interview questions on Angular 2, get a look at them and enhance your knowledge.

Key Features of Angular 2

Below are few major features of Angular 2



Highly scalable

Practice Best Angular 2 Interview Questions and Answers;

Q1. What are angular2 modules?

An Angular2 module is a deployment sub-set of your whole Angular application. An Angular2 module is basically a mechanism to group components, directives, pipes, and services that are related, in such a way that can be combined with other modules to create an application. It is used to put logical boundaries in an application and also for splitting up an application into smaller parts and lazy load each separately, and to create libraries of components that can be easily imported into other applications.

Q2. Which programming language is used with Angular2?

Typescript programming language is the programming language that is used with Angular2 as it allows the Angular 2 developers to do their JavaScript work in TypeScript.

Q3. Does angular 2 use webpack?

Yes, Angular 2 uses webpack but only behind the scenes to transpile TypeScript to JavaScript, transform Sass files to CSS, and many other tasks. WebPack is a module bundler and loader, the application needs to create a separate file where import statements for all required modules for the application are defined.

Q4. Explain how routing in angular2 works?

In Angular2, Routing is a process of changing the state of your Application by loading different components depending upon the URL that the user enters. It helps in directing users to different pages based on the option they choose on the main page which is based on the option they choose. It basically helps us navigate from one view to another as users perform tasks in web apps.

Q5. How to destroy a component in Angular2?

You can destroy a component in Angular2 by calling the component's ngOnDestroy() lifecycle hook when the page unloads. This is done by leveraging the host page's life cycle.

Q6. What is observable in Angular2?

In Angular2, Observable is a more powerful way of handling HTTP asynchronous requests. An observable is like a stream that allows passing zero or more events where the callback is called for each event. It works with multiple values for a particular time and supports map, filter, reduces, and similar operators.

Q7. What is decorator?

In Angular2, the Decorators are a new feature of TypeScript and used throughout the Angular code. Decorators are basically a design pattern that is used to separate modification or decoration of a class without modifying the original source code. In AngularJS, decorators are functions that allow a service, directive or filter to be modified prior to its usage.

Q8. How angular2 is different from Angular1?

The major difference between Angular2 and Angular1 can be stated as follows:

  • Angular 2 is not an updated version of Angular 1 but it is completely rewritten.
  • Angular 2 uses TypeScript which is a superset of JavaScript.
  • Angular 1.x was not built with mobile support in mind, where Angular 2 is mobile-oriented.
  • Angular 1's core concept was $scope but you will not find $scope in Angular 2.0 and above.
  • Angular 1.x Controllers are gone in Angular v2. We can say that Controllers are replaced with “Components” in Angular 2.
  • In Angular 2, Structural directives syntax is changed. ng-repeat is replaced with *ngFor.
  • In Angular 2, local variables are defined using the hash(#) prefix.
  • Angular 2 uses a Hierarchical Dependency Injection system which is the major performance booster.
  • Angular 2 implements unidirectional-tree-based change detection which, again, increases the performance.


Q9. Explain what is lazy loading in Angular2?

In Angular2, Lazy loading is a module that is used to decrease the start-up time. When lazy is used, then our system application does not need to load everything at once. It only needs to load what the user expects to see when the application first loads. It improves the performance of our system applications and keeps the initial payload small and these smaller payloads lead to faster download speeds. 

Q10. What is the difference between observable and promises?

Observable - An observable is like a stream that allows passing zero or more events where the callback is called for each event. Observable is a more powerful way of handling HTTP asynchronous requests. It works with multiple values for a particular time and supports map, filter, reduces, and similar operators.

Promise - A promise is a placeholder for a future value. It handles a single event when an asynchronous operation completes or fails and also serves the same function as callbacks but has a nicer syntax and makes it easier to handle errors.handles a single event when an asynchronous operation completes or fails.

Q11. What are Pipes in Angular 2?

In Angular, Pipes are one of the most useful features that are also known as filters in Angular 2. Pipes allow us to change the data inside the template as it provides a simple way to transform values in an Angular template. Generally, a pipe takes the data and transforms this input to the desired output which means it takes in a value or values and then returns a value. Angular2 consists of several inbuilt pipes and you can also build your own pipes.

Q12. How to use a Route Guard? Can you list few?

Angular’s route guards are interfaces that can tell the router whether or not it should allow navigation to a requested route. It can be used by making the decision by looking for a true or false return value from a class that implements the given guard interface. There are five different types of route guards, these are as follows:

  • CanActivate
  • CanActivateChild
  • CanDeactivate
  • CanLoad
  • Resolve


Q13. For what is <router-outlet> is used for?

In Angular, Router-outlet works as a placeholder which is used to load the different components dynamically based on the activated component or current route state. emits an activate event when a new component is instantiated, and a deactivate event when a component is destroyed.

Q14. What is the advantage of using FormBuilder in Angular2?

The advantage of using FormBuilder in Angular2 is that the FormBuilder provides syntactic sugar that shortens creating instances of a FormControl, FormGroup, or FormArray. The FormBuilder is the helper API to build forms in Angular and reduces the amount of boilerplate needed to build complex forms.

Q15. What is RxJS?

RxJS stands for Reactive Extensions for JavaScript, which is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code. RxJS can be used with other Javascript libraries and frameworks and also provides an implementation of the Observable type, which is needed until the type becomes part of the language and until browsers support it.

Q16. How do you define a wildcare state in Angular2?

You can simply define a wildcard state in Angular2 with the help of two asterisks, ** as it indicates to Angular that the definition of this route is a wildcard route.

Q17. What do you know about AOT?

In Angular AOT stands for ahead-of-time. It compiles your app at build time on the server and converts your Angular HTML and TypeScript code into efficient JavaScript code during the build phase before the browser downloads and runs that code. AOT is much suitable in the case of Production mode.

Q18. What is TestBed?

In Angular, the TestBed is the primary API for writing unit tests for Angular applications and libraries. It is the first and largest of the Angular testing utilities. It creates an Angular testing module — a @NgModule class — that you configure with the configureTestingModule method to produce the module environment for the class you want to test.

Q19. How would you select all the child components in Angular2?

You can use @ViewChild decorator. The @ViewChild also provides an instance of other components or directives in a parent component so the parent component can access the methods of that component or directive.

Angular Vs React. Which one is better?



It is a framework

It is a library

It has complete functionality MVC

It possesses very few layers

Angular provides large support for 3rd party libraries

It is very flexible

Codes are shorter and easy to understand as it follows the template approach for HTML

HTML is written in JS which makes it confusing

Angular is very fast respected to development time

It is tedious at times

It follows the two-way data binding process

It has a one-way data binding process

Pros and Cons of Angular

  • Support for web components: Unlike the AngularJS having a closed system for modularizing, Angular2's foundation is basically to lie on the rising web components standard. By this, it is able to use AngularJS directly. Therefore, it does not need any wrapper coding, any component written as a Web Component.
  • Component-based architecture: It is the biggest change that shifts AngularJS to Angular 2. Angular 2 supports the components which are the small pieces of the interfaces that are independent of each other. AngularJS took a long time to make HTML elements and requires the developer to reason about directives, controller, etc. But, Angular 2 simplifies this process with reusable UI building blocks known as components, which are easy to test and reuse.
  • Reusability: Components that are similar to each other are well encapsulated, simply put, self-sufficient. It helps the developers in reusing them across various parts of an application. It is also beneficially in enterprise-scope applications where various system converges but may possess many similar elements like data pickers, search boxed, sorting lists, etc.
  • Faster and Modern Browsers: In modern days, developers demand faster and modern browsers. Developers desire AngularJS 2.0 stress more on browsers like IE10/11, Firefox, Chrome, Safari and Opera on the desktop and Chrome on Android, iOS6, Windows phone 8+ and Firefox mobile. It is believed that this would permit AngularJS codebase to be short and compact. It is able to support the new and great features without bothering about backward compatibility and polyfills. As a result, the AngularJS app development process would be simplified.
  • Strong and Flexible Routing: A wide variety of needs and requirements are supported by routing like child and sibling states which bring some features like nested states and sibling views with version 2.0 in the core AngularJS router. There are some great and extensive features like URL resolver, navigation model, hash change, push state child router or location service, etc. which could redo the routing and as a result make it simple, scalable and extensible.

Cons of Angular

  • The divided and churning community: In spite of the LTS claims, it is the community around any technology which makes it strong in the market but the Angular community is doubtful. According to the survey, Angular is the second most commonly used technology in the category Frameworks, Libraries, and Other Technologies, which is great.
  • Typescript: We know that Angular 2 is written in Typescript, but it has some prerequisites such as knowledge of OOPs. It is quite difficult to handle it if you don't have a good knowledge of OOPs. Some developers have faced this drawback as they have to make more efforts to work on Angular 2.
  • Not an update, a change: Angular 2 is known as an updated version of Angular JS, instead, it seems like a new system. It is not easy to get used to Angular 2, because it is not a small release, but a game changer.
  • Steep learning curve: In comparison with the other framework like React or Vue, it is difficult to onboard new developers familiar with JavaScript to learn and use the Angular. Another main problem is RxJS which is a reactive programming library for asynchronous programming. It is very important to learn it at least at the basic level.
  • Angular is verbose and complex: One of the main disadvantages of the Angular is that it is verbose and complex. This problem can also be seen in the AngularJS which is not even solved in Angular 2. Many developers do complain about the verbosity of the instrument.

About Author :

  • Author of Angular 2 Interview Questions

    Sharad Jaiswal

    My name is Sharad Jaiswal, and I am the founder of Conax web Solutions. My tech stacks are PHP, NodeJS, Angular, React. I love to write technical articles and programming blogs.

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