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Angular 4 Interview Questions

Angular 4 Interview Questions

Angular 4, released in March 2017, is a JavaScript framework for building apps in HTML, JavaScript, and TypeScript. Angular 4 offers built-in features for HTTP service, animation, and materials. This is an essential topic in the Angular 4 Interview Questions for experienced professionals. The unique feature in Angular 4 is that starting from Angular 4, developers will be able to query ParamMap in the router.

Quick Overview of Angular 4

Angular 4
What is Angular 4? This version released in March 2017, is a JavaScript framework for building apps in HTML, JavaScript, and TypeScript. It offers built-in features for HTTP service, animation, and materials.
Latest Version Angular 8.0. released on May 28, 2019
Created By Google
Written in TypeScript
Official Website https://angular.io/

This means a request for the route- and the query parameter can be assigned to a route. Until Angular 2, route parameters were stored in a key-value object and were accessible through standard JavaScript syntax. Do you want to succeed in your Angular 4 Interview Questions and Answers? Read on!

Another unique feature is that the functions that were necessary for animations are placed in their package. This has been done to avoid creating unnecessary bundles of significant size. Until Angular 2, these functions were offered as part of the core module and were always included even if they were not getting used in apps.

In angular 4, the use of decorators is done extensively for compiling the code. There are four types of decorators – Class, Property, Method, and Parameter.

Type security and speed ngc-Compilerhave improved in Angular 4 as compared to Angular 2. If you are scrolling on the web for angular 4 interview questions and answers pdf, then this guide will gonna help you.

Related Interview Questions on Angular.

Here is the list of top 50 angular 4 interview questions. Now you can crack your angular interview with the help of these questions.

Last update: 05 Oct 2019, 36 Questions and Answers

Most Frequently Asked Angular 4 Interview Questions And Answers With Examples:

In general, deep linking takes a specific page directly without searching and traversing application from the landing page. It helps in generating and getting indexes so that the specific links can be easily searched by the search engines.
Angular 4 support deep linking using ‘#’

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Following steps will provide you the proper direction to use priming in angular 4
  • In order to install primeng UI libraries or primeng UT components: Install primeng using the command- npm install primeng-save
  • In dependencies section include package.json
  • Goes to the setting, and configure PrimeNG in app.module.ts
  • Include import { DataListModule } from ‘primeng/primeng;
  • Import DataListModule and include primeng components using command bikes.component.html
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Angular 4 is fast compared to its previous versions due to various reasons. Here are some of them mentioned below:

  • It reduces the size of generated code bundle up to 60%.
  • The animation part moved out to a separated package @angular/animations
  • It is backward compatible.
  • Introduction of proper disapproval phases for easy adjustment of codes.
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Angular 4 is the upgraded version of AngularJS, which is the very first introduction of AngularJS. The newer version Angular 4 has fulfilled several drawbacks of its predecessor and introduced excellent features such as Router ParamMap support, Dynamic Components with NgComponentOutlet, latest TypeScript functions, simplified HTTP request, better Animation package, mobile-oriented framework, server-side run and more, which were are not available with the AngularJS.

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While creating an Angular 4 component, a shadow DOM is created by default and our template gets loaded into it. It’s a DOM element subtree which renders as part of the document but not into the present main document DOM tree. It is used by browsers to determine the rendered object on the page. JavaScript programs use it to modify content, page styling and structuring.

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To debug Angular 4 projects using visual studio 2017, we have to follow the below-mentioned steps.
  • Create our project as Asp.Net Core Web Application and use the “Angular” project template.
  • Next to "IIS Express", click the down-arrow to set the web browser to Google Chrome.
  • Run debugging and the script debugging being enabled message will pop up by Chrome.
  • Continue further by setting a breakpoint on "this.currentCount++;"in counter.component.ts.
  • Now visit the Counter screen to click Increment and the breakpoint set will be hit.
  • While performing this, make sure to turn off the Chrome Developer Tool running

Note- make sure that your chrome developer tools will run on the same time during the process of debugging

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In general, angular 4 providers are the injectors that inject the objects by the providers, not components and services. Angular 4 providers different types of provides namely class provider, value provider, factory provider, and alias provider, etc. additionally, angular 4 providers can be configured at component and module level.

We can configure and change the services using providers with the use of syntax-

Providers: [
    {provide: AniimalServices, useClass: Animal Service }
]

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Angular 4 services contain functions or methods that consistently maintain the data of an application throughout its life which implies that data will remain secure and available at all time. The main aim of angular 4 services is to share business logic, data, information, models with several components of angular 4 applications.

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We need Ngmodel in angular 4, as it possesses the property of binding and encapsulating the input elements of DOM. In short, we need Ngmodel in angular 4 for two –way-data-binding process.

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Angular 4 is an advanced JavaScript framework which uses HTML, JavaScript, and TypeScript web applications and APK apps. It’s a superset of JavaScript and offers excellent built-in features for HTTP service, animation, navigation, menus, toolbar, materials, etc.

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Angular 4 has several new feature additions. As most of the changes are implemented to the background rather than its core functionality of coding, it’s being called an invisible makeover to its previous version. The compiler error messages have improved as well as the code generation. According to the Angular team, patches will be released every week. All the major releases will be followed with minor Angular release. In every six months, there will be a significant release for the framework which will be easy to integrate breaking changes. It also has the potential to improve performance when used appropriately. The structure now also supports TypeScript 2.1+.

New features in Angular 4.
  • TypeScript Compatibility
  • Dynamic Components
  • Source Maps for Templates
  • Router ParamMap
  • AOT Compilation
  • Revamped *ngIf and *ng For
  • Animations Package
  • Angular Universal
  • Flat ES Modules
  • Smaller and Quick
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Here are a few significant differences between Angular 2 and 4 which developers are going to notice.
  • Angular 4 has many inbuilt animation packages which were missing in Angular 2.
  • Angular 4 has its template tag called “ng-template.” The previous version uses only “template.”
  • Compared to Angular 2, in the newest version, developers can use else syntax with Nglf for excellent UI handling.
  • A new template syntax addition “as keyword” in Angular 4 which can be used to simplify to the “let” syntax.
  • Simplified “HTTP request” and application testing in Angular 4.
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AngularJS is the very first version of the Angular. A tool named AngularCLI is used to generate Angular components. Angular JS which is a client-side framework works with JavaScript and still supported but not compatible with Angular any more. Simplifying it, AngularJS is the old version and Angular is the newest one.

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To set Http Request Header in Angular 2, create the HTTP Client Injectable class and inject the HttpClient object in the Component. Developers use HTTP Interceptors to set Http Request Header in Angular 4. To achieve this. Write an interceptor for adds a header for every request and after creating the interceptor, register it using HTTP_INTERCEPTORS in the @NgModule().

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To create a new component in Angular 4 using CLI,
  • Open Project Directory
  • Run any one of the below mentioned the syntax

We have the most extensive question bank to help you answer Angular 4 interview questions and answers.

Example

                                                    

ng component name

or

ng generate component componentname

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No coding level changes are required to enhance a project present in Angular 2 to Angular 4. Users only have to update the tsconfig.json and package.json files. Some minor adjustments may be needed depending on project types. After updating the data, clean out your node_modules directory, run npm install and npm start and you will be started with the Angular 4.

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If Else statement in Angular 4 can be written using following syntax-
Open /src/app/app.components.ts:
Export class AppComponent {
Title – ‘app works!;
}

Open /src/app/app.component.html
<div *ngIf = “ title; else login”>
The user is logged in. </div>
<ng-template #login> in order to login pleae continue. </ng-template>
Then statement can be write using following syntax-
<div *ngIf = “title; then logout else login “> </div>
<ng-template #login> please login to continue . </ng-template>
<ng-template #logout> Hi abc, <button> logout now </button> . </ng-template>
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In Angular 4, the ForRoot method is used when the module is "eager," not lazy-loaded. Except for lazy modules which loaded on-demand with their factory, Angular creates a factory for all other modules. The ForRoot method allows users to access providers from any point in the application that is not lazy-loaded. This ultimately will enable users to have different configurations for different load cases.

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Angular 5 has plenty of new features. Few of the most important ones are mentioned below:
  • Addition of a build optimizer which removes unnecessary applications and codes.
  • Support for DOM and Angular Universal State Transfer API.
  • Optimized standardization across various browsers.
  • Addition of a new HttpClient and lifecycle events router.
  • Creation of Angular 5 projects by default with CLI 1.5.
  • Multiple name support for directives and components.
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Compared to Angular 4, Angular 5 has plenty of feature additions, bug fixes and service improvements implemented to it. The addition of a build optimizer to Angular 5 is a pleasant surprise for developers. Added to CLI, this tool can help developers to create smaller bundles for the application. It also increases the boot speed of the application for users. Few other crucial differences between these two versions will be compiler improvements, the addition of HttpClient and new router lifecycle events. All these features have newly included to the Angular 5.

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There are various ways available to install Angular 4.
  • Install the Angular CLI
    npm install -g @angular/cli
  • Create a Project
    ng new MyApp
  • Serve the application
    cd MyApp
    ng serve --open

This information can be asked during angular 4 interview questions.

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In Angular 4, components have their view, whereas directives are just “behavior” added to the existing components and elements. Simplifying it, components extend directives. There can be many directives on a host element, but only one component.

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Unit testing or private testing is used to test the system’s components. This process is s best practice to test small separate pieces of code. If the unit testing depends on any of the external resources such as networks, APIs and databases, then it won’t be listed as a unit test.

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In Angular 4, template reference variables allow users to access an instance of a directive or component or a DOM present in the template. These are defined by a hash sign (#) combined with a name as an additional DOM element’s attribute.

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In Angular 4, data binding is a core concept that allows defining communication between the DOM and a component. This makes it easy to define interactive applications without complexion of pulling and pushing data.

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In Angular 4, there are four types of component decorators:
  • Class decorators
  • Property decorators – used for properties inside classes
  • Method decorators – used for methods inside classes
  • Parameter decorators – used for parameters inside class constructors

This information is usually asked in interview questions on Angular 4.

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In AngularJS, JSON Web Token is used to send information which can be trusted and verified using a digital signature. The JSON Web Token comprises a URL-safe and compact JSON object, which is cryptographically signed to verify its authenticity. This also can be encrypted if the payload contains any sensitive information.

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Yes, angular 4 services is a compiler which transverse the DOM looking for attributes. The process of compilation is partitioned into two phases namely-

Compile- means to traverse the DOM and gather all directives such as ng-repeat.

Link- means to produce a live view by combining the directives with a scope.

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ElementRef is basically a class or reference types used for abstraction. The class structure holds the native elements and ElementRef is used to access the native elements

@Component({
selector: 'sample',
...export class SampleComponent{
constructor(private hostElement: ElementRef) {
   //outputs
   console.log(this.hostElement.nativeElement.outerHTML);
}

ElementRef is used to break the abreaction rather than using specific API DOM like textContent

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The embedded view is a component or it is a hosting component which is used to define the template.

Example

                                                    

abstract class EmbeddedViewRef<C> extends ViewRef {
      abstract context: C abstract rootNodes: any[]
}

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Traceur compiler is compilers which use ECMAScript Edition 6 (ES6) that compiles the regular javascript which runs on user’s search engine.

Number of ways to use traceur compiler.
  • Typing ES6 code in the page Read-eval-print-loop.
  • In web page include Traceur and compile ES6 script content on the fly.
  • Use node to compile ES6 to ES5 offline.
  • Include the result in Web pages or just execute the result in angular 4.
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JavaScript

JavaScript is a programming language designed for web pages. It is developed by Netscape and Sun and it is initiated by Netscape and called LiveScript. It is used to enhance web pages with dynamic and interactive features.

ECMAScript

ECMA is an abbreviated form of European Computer Manufacturer's association. In general, ECMAScript is a standard used in scripting languages such as Jscript, JavaScript.

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There are three types of loading namely eager loading, lazy loading, and preloading. In general, eager loading is a module which needs to import into the Angular 4 application module by importing metadata of @NgModule decorator. Additionally, eagerly loading is useful for small size angular applications in which all feature modules will be loaded before starting of the application.

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In order to create block component dynamically, it is important to import following AppComponent such as-

  • ViewContainerRef, ComponentFactoryResolver and ViewChild from @angular/core
  • MessageComponent from message.component.
  • ComponentFactory and ComponentRef from@angular/core

Example

                                                    

import {
   Component,
   ViewContainerRef,
   ViewChild,
  ComponentFactoryResolver,
  ComponentRef,
  ComponentFactory
}

from '@angular/core';
import { MessageComponent } from './message.component';
@Component(
{
   selector: 'app-root',
   templateUrl: './app.component.html'
}
)
export class AppComponent {
  title = 'app';
}

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We can use the ngx-cookie-service node package to save cookies in Angular 4.

Use the following steps:
  • Install the node package with the following syntax:
    npm install ngx-cookie-service –save
  • Now, we have to add the cookies service to app.module.ts as a provider.
    @NgModule({
        ...,
        providers: [ CookieService ]
    })
  • Further, continue by importing and injecting it into a component.
    import { CookieService } from 'ngx-cookie-service';
    constructor( private cookieService: CookieService ) { }
    ngOnInit(): void {
    this.cookieService.set( 'Test', 'Hello World' );
    this.cookieValue = this.cookieService.get('Test');

    }
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