Angular 2 Interview Questions

Angular 2 Interview Questions

Dear friends, below are the list of Angular 2 interview questions that have been designed for Angular 2 programmers / UI Developers who are preparing interviews on Angular2 interviews. Here, we have added some basic and advanced or both questions on Angular 2 that are asked in 2018 and that help you to crack interview on Angular 2.0. You can also download latest Angular2 interview questions and answers pdf for freshers and experienced.

Angular2 is a free open source component-based UI Framework from google web development team re-written in TypeScript ( Superset of JavaScript ).

Below are the list of Top 37 Angular 2.0 interview questions and answers.

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Angular 2 Interview Questions

Angular 2 is a completely revived component-based Javascript framework in which an application is a tree of loosely coupled components. It is a more advanced version of angularJS. It is more of an "all in one" framework so it also helps in creating a single website without getting trapped into different JS frameworks. An Angular 2 is a modular framework in which our code is divided into individual procedures that offer a similar kind of functionality, hence improving the testing, up gradation and maintenance of the application. It has a lot of useful features such as- server-side rendering, cross-platform, and supports more languages than any other framework. It is a new typescript framework built around the concept of components which is paving the way for a better and spacious development. We can even make hybrid applications using Angular 2 which gives us a sharp edge by providing us the flexibility to use the same standard codes for developing other applications.

In Angular 2, decorators are used as an identifier of class or type of the object that is created by the TypeScript.The Angular 2 identifies the class below decorator call as the definition of the class and extends the decorator specific properties with the class definition.

The hidden property in Angular 2 is a special case.

  • The property is more powerful and is used to bind any property of the elements.
  • It is considered the closest cousin of ngshow and nghide.
  • It sets the display property “display: none”.

The template in Angular 2 is used to define the views of the AngularJS Application.

The Angular 2 comprises of the following key components:

  • Module – This is used to break the application into the logical pieces of the program code and each piece of code or module is designed to perform a single and unique task.
  • Component – This is used to bring the modules together.
  • Templates – This is used to define the Views of an Angular JS application.
  • Metadata – This is used to add more data to an Angular JS application.
  • Service – This component is used to develop the components, which can be used to share in the entire application.

The component lifecycle hooks overview the life cycle sequence and the interfaces. Angular manages the life cycle of a component. Angular creates it, renders it. It can also create and render its children. It also checks when its data-bound properties change. It can even destroy it before removing it from the DOM. The life cycle hook offered by angular provides the visibility into these key life moments and the ability to act when they occur. The components go through an entire set of processes or life cycle right from its initiation to the end of the application.

There are a number of lifecycle hooks which are listed below:–

  1. ngOnChanges
  2. ngOnInit
  3. ngDoCheck
  4. ngAfterContentInit
  5. ngAfterContentChecked
  6. ngAfterViewInit
  7. ngAfterViewChecked
  8. ngOnDestroy

Lazy loading is a module which 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. The modules which are lazily loaded will only be loaded when the user navigates to their routes. Lazy loading improves the performance of our system applications. It keeps the initial payload small and these smaller payloads lead to faster download speeds. It helps in lowering the resource cost, especially on mobile networks. If a user doesn’t visit a section of the application, they won’t ever download those resources. The concept of lazy loading in angular requires us to format the application in a certain way. All the assets that are to be lazy loaded should be added to its own module. Lazy loading is setup in the main routing file. Lazy loading overcomes the problem of slow loading of applications in their own way which hence improves the loading time of the application.

Lazy loading can be done only in four steps:–

  1. Update your route file
  2. Install angular-router-loader and add the loader to your webpack configuration file.
  3. Define the lazy routes
  4. Import the routes to the module.

Shared module is used to import the services in both eager and lazy loaded module. We all know that lazy loaded modules create their own branch on the dependency injection tree. Shared module consists of the services that are registered by the angular in the root app injector. For this, we need not import it in the lazy module because lazy loaded modules already have access to the services defined at the root. Components, pipes and directives are also defined in the shared module. Other modules that import the shared module can use it in their templates. This means that the modules can be imported normally in the lazy loaded module. The shared module contains the code that will be used across the applications and featured modules. It also consists of the common template components. “Dumb components” should also be present in the shared module. It typically consists of some common angular modules too. When you are importing the shared module, you will also need to import the module with its providers, because there is no app module in the test.

Caching of an observable data is done with the help of “observable.cache”. We can use caching in order to cache the response in the memory and then, on the next subscription, instead of requesting the remote server again. This operator is used at the end of the string. Caching is important for the performance, especially on bandwidth restricted devices and slow networks. You should have a good understanding of caching while working with promises but while translating it to observable, it is a bit difficult. Therefore, when interacting with observables, we typically set up a subscription on the consumer side and react to values coming through the pipe. We can easily add caching to the observables by adding publishReplay(1) and refCount.

Constructors are used for initializing class members and also for dependency injection. Ngonlnit is used for the initialization work. Both of these methods are called when the component is created. It is really important that we should know, when to and how to use them. These are used for providing the best structure for your component’s code. A constructor method is a pre-defined method in the constructor class which is only called when the class is instantiated. It is also used for properly initializing the fields. The constructor in Angular 2 is used to create a new instance of the class. Ngonlnit is the class we import when we implement the constructor in order to use it in a class. The method used in this case is ngOnlnit(). This method helps in initializing the directive or the component after the data-bound properties are displayed and the directive or components input is set.

Angular supports most of the recent browsers some of which are:

  • Google Chrome
  • Firefox
  • Edge
  • IE for versions 9-11
  • Safari
  • iOS 7.1
  • Android 4.1
  • IE Mobile

Components in Angular 2 are simply directives that are always associated with a direct template. Angular 2 components have an extremely well defined life-cycle. When working with angular components, we can make use of interfaces which allows us to implement functionality for different times in a components lifecycle. A component must belong to an NgModule in order for it to be usable by another component or application. Components can even control their runtime behaviour by implementing various Life-cycle hooks.

Declaration of component:

@component ({selector: 'great', template: 'hello {{name}}!'})

Class greet{

Name: string = 'world';

}

Components always have a template and only one component can be instantiated per an element in a template. When a component is instantiated, angular creates a change detector, which is responsible for propagating the component’s building.

Angular 2 is a re-written version of Angular1 and not an update. The best way to compare Angular 2 and Angular 1 is by finding out the new features in Angular 2. This way we will be able to find out the advantages of Angular 2 over Angular1 precisely. So, some of the advantages of Angular 2 are:-

Angular 2Angular1
Angular 2 is a mobile-oriented frameworkWhereas Angular1 was not developed with mobile base in mind.
Angular 2 is a versatile framework, i.e. we have more choices for languages. We can use ES5, ES6, Typescript or Dart to write an Angular 2 codeWhereas an Angular1 code can written by using only ES5, ES6 and Dart. We don’t have many choices of language in Angular1.
Nowadays, the controllers are replaced by components and Angular 2 is completely component based.Whereas Angular1 was based on controllers whose scope is now over.

Angular 2 directly uses the valid HTML DOM element properties and events which reduces the usage of many available built-in directives.

No, currently there is not any such tool available that ports the Angular 1 code to the Angular 2 code.
In the process of porting, the Angular 1 code to Angular 2, the side by side manual conversion of Angular 1 directives to the Angular 2 components takes place because they are two different frameworks and hence requires different approaches to solve the same problem.

Also, Read: 80 Best AngularJs interview Questions

The Angular 2 Applications provide with the option of error handling.The errors in Angular 2 can be handled by including the React JS catch library and later using the catch function.

  • The catch function, which is used after adding the catch library contains the link to the Error handler function.
  • And in this error, handler function, the errors are sent to the error console, and also the errors are thrown back to continue the execution.
  • So, whenever an error occurs it will be redirected to the error console of the web.