Mastering the Top 16 Angular 7 Interview Questions for 2024

As the demand for skilled Angular developers continues to rise, acing the interview process has become crucial for landing your dream job. In this comprehensive guide, we’ll explore the top 16 Angular 7 interview questions that you should be prepared to tackle in 2022.

1. What is Angular 7, and how is it different from AngularJS?

Angular 7 is the latest version of the popular Angular framework, released in October 2018. It is a complete rewrite of AngularJS, the framework’s previous iteration. Unlike AngularJS, which was built using JavaScript, Angular 7 is written entirely in TypeScript, a superset of JavaScript. This change brings several benefits, including better tooling, improved developer productivity, and enhanced code maintainability.

Angular 7 also introduces several new features and improvements, such as:

• Angular CLI Prompts
• Angular Ivy Renderer (Optional)
• Drag and Drop Features
• Virtual Scrolling
• Improved Routing
• Improved Performance

2. What is the purpose of the ngOnInit lifecycle hook?

The ngOnInit is a lifecycle hook in Angular that is called after the component has been initialized. It is primarily used for initialization tasks, such as fetching data from a service or performing any necessary setup operations. This hook is an excellent place to perform tasks that need to be executed only once during the component’s lifetime.

Here’s an example of how you can use the ngOnInit hook:

import { Component, OnInit } from '@angular/core';@Component({  selector: 'app-example',  template: `    <h1>{{ title }}</h1>  `})export class ExampleComponent implements OnInit {  title: string;  constructor() { }  ngOnInit() {    // Fetch data or perform initialization tasks here    this.title = 'Hello, Angular!';  }}

3. What are directives in Angular 7, and what are the different types?

Directives are one of the core building blocks of Angular applications. They are classes that add additional behavior to elements in the Angular template. Angular provides three types of directives:

1. Components: These are directives with a template. They are typically used to create UI elements and manage their behavior.

2. Structural Directives: These directives are responsible for changing the structure of the DOM by adding, removing, or manipulating elements. Examples include *ngIf, *ngFor, and *ngSwitch.

3. Attribute Directives: These directives change the appearance or behavior of an element, component, or another directive. Examples include ngStyle, ngClass, and custom directives created by developers.

4. Explain the difference between AngularJS and Angular.

AngularJS (version 1.x) and Angular (version 2+) are two different versions of the Angular framework. While they share some similarities, there are several key differences:

One of the most significant differences is that Angular is a complete rewrite of AngularJS, with a focus on performance, scalability, and maintainability.

5. What are services in Angular 7, and how are they used?

Services in Angular 7 are reusable classes that encapsulate specific functionality or data. They are used to share data or logic across multiple components in an application. Services can be injected into components, allowing for better separation of concerns and promoting code reusability.

Here’s an example of how to create and use a service in Angular 7:

// my-service.service.tsimport { Injectable } from '@angular/core';@Injectable({  providedIn: 'root'})export class MyService {  data: string = 'Hello, Angular!';  getData() {    return this.data;  }}// my-component.component.tsimport { Component } from '@angular/core';import { MyService } from './my-service.service';@Component({  selector: 'app-my-component',  template: `    <h1>{{ serviceData }}</h1>  `})export class MyComponent {  serviceData: string;  constructor(private myService: MyService) {    this.serviceData = this.myService.getData();  }}

In this example, the MyService service is injected into the MyComponent component, allowing the component to access the service’s data and methods.

6. What is the purpose of the ngOnChanges lifecycle hook?

The ngOnChanges lifecycle hook is called whenever one or more data-bound properties of a component have changed. This hook is primarily used to perform actions in response to changes in input properties.

The ngOnChanges hook receives a SimpleChanges object that contains the previous and current values of the input properties that have changed. This object can be used to determine which properties have changed and perform the necessary actions.

Here’s an example of how you can use the ngOnChanges hook:

import { Component, Input, OnChanges, SimpleChanges } from '@angular/core';@Component({  selector: 'app-example',  template: `    <h1>{{ title }}</h1>  `})export class ExampleComponent implements OnChanges {  @Input() title: string;  ngOnChanges(changes: SimpleChanges) {    if (changes.title) {      // Perform actions when the 'title' input property changes      console.log('Title changed:', changes.title.currentValue);    }  }}

In this example, the ngOnChanges hook is called whenever the title input property changes. The changes object contains the previous and current values of the title property, which can be accessed via changes.title.previousValue and changes.title.currentValue, respectively.

7. What is the purpose of the ngAfterViewInit lifecycle hook?

The ngAfterViewInit lifecycle hook is called after the component’s view (and its child views) have been initialized. This hook is useful when you need to perform operations that involve the component’s view or child views.

Some common use cases for the ngAfterViewInit hook include:

• Accessing and manipulating DOM elements
• Performing calculations based on rendered view elements
• Integrating with third-party libraries that require access to the rendered view

Here’s an example of how you can use the ngAfterViewInit hook:

import { Component, AfterViewInit, ViewChild, ElementRef } from '@angular/core';@Component({  selector: 'app-example',  template: `    <h1 #headingRef>{{ title }}</h1>  `})export class ExampleComponent implements AfterViewInit {  @ViewChild('headingRef', { static: false }) headingRef: ElementRef;  title: string = 'Hello, Angular!';  ngAfterViewInit() {    // Perform operations after the view has been initialized    this.headingRef.nativeElement.style.color = 'red';  }}

In this example, the ngAfterViewInit hook is used to access the rendered <h1> element and change its color to red using the ViewChild decorator and the ElementRef class.

8. Explain the concept of dependency injection in Angular 7.

Dependency injection is a design pattern that allows objects to receive instances of their dependencies instead of creating them themselves. In Angular 7, dependency injection is a core feature that facilitates the creation of reusable, testable, and maintainable code.

Angular’s dependency injection system provides a way to create and manage dependencies, making it easier to develop and test components in isolation. Dependencies can be injected into components, services, directives, and even other services.

Here’s an example of how dependency injection works in Angular 7:

// my-service.service.tsimport { Injectable } from '@angular/core';@Injectable({  providedIn: 'root'})export class MyService {  getData() {    // Service logic  }}// my-component.component.tsimport { Component } from '@angular/core';import { MyService } from './my-service.service';@Component({  selector: 'app-my-component',  template: `    <!-- Component template -->  `})export class MyComponent {  constructor(private myService: MyService) { }  // Component logic that uses MyService}

In this example, the MyService service is injected into the MyComponent component through the constructor. Angular’s dependency injection system takes care of creating and providing the service instance to the component.

9. What are pipes in Angular 7, and how are they used?

Pipes in Angular 7 are simple functions that transform input data into a desired output format. They are commonly used to format dates, numbers, strings, or apply other transformations to data before displaying it in the view.

Angular provides several built-in pipes, such as DatePipe, UpperCasePipe, LowerCasePipe, and CurrencyPipe. Additionally, developers can create custom pipes to suit their specific needs.

Here’s an example of how to use pipes in Angular 7:

<!-- my-component.component.html --><p>Today's date: {{ currentDate | date }}</p><p>Product price: {{ price | currency:'USD' }}</p><p>User name: {{ userName | uppercase }}</p>

// my-component.component.tsimport { Component } from '@angular