Interview Questions

1. What are the different types of directives in Angular?

There are mainly three types of directives in Angular:

Component Directives: The component directives are used to form the main class in directives. To declare these directives, we have to use the @Component decorator instead of the @Directive decorator. These directives have a view, a stylesheet, and a selector property.

Structural directives: These directives are generally used to manipulate DOM elements. The structural directive has a ' * ' sign before them. We can apply these directives to any DOM element.

Following are some examples of built-in structural directives:

*ngIf Structural Directive: *ngIf is used to check a Boolean value and if it's truthy, the div element will be displayed.

<div *ngIf="isReady" class="display_name">  



*ngFor Structural Directive: *ngFor is used to iterate over a list and display each item of the list.

<div class="details" *ngFor="let x of details" >  


    <p> {{x.address}}</p>  



Attribute Directives: The attribute directives are used to change the look and behavior of a DOM element. Let's create an attribute directive to understand it well:

This is how we can create a custom directive:

Go to the command terminal, navigate to the directory of the angular app and type the following command to generate a directive:

  • ng g directive yellowBackground   

This will generate the following directive. Manipulate the directive to look like this:

import { Directive, ElementRef } from '@angular/core';  


 selector: '[appYellowBackground]'  


export class YellowBackgroundDirective {  

 constructor(el:ElementRef) { = "yellow";  



Now, you can easily apply the above directive to any DOM element:

<p appYellowBackground>Hello JavaTpoint</p>  

By Md Riyazuddin 2 0
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