Angular Interview Questions

In Angular, a template is defined as part of a component and describes the view for that component. Templates are written using HTML and can include Angular-specific syntax for binding data, conditionally displaying content, and handling user events. There are two main ways to define a template in Angular: inline templates and external templates.

1. Inline Template:

• Definition: An inline template is defined directly within the @Component decorator using the template property.
• Purpose: Useful for simple or small templates where defining the HTML directly in the component makes the code more concise and contained.
• Example:

  import { Component } from '@angular/core';
  
  @Component({
    selector: 'app-inline-template',
    template: `
      <h1>{{ title }}</h1>
      <p>Welcome to the inline template example.</p>
    `,
    styles: [`
      h1 { color: blue; }
    `]
  })
  export class InlineTemplateComponent {
    title: string = 'Hello, Angular!';
  }

2. External Template:

• Definition: An external template is defined in a separate HTML file and referenced in the @Component decorator using the templateUrl property.
• Purpose: Ideal for larger or more complex templates, promoting better separation of concerns and making the component class cleaner and easier to manage.
• Example:
  • Component Class (TypeScript):

    import { Component } from '@angular/core';
    
    @Component({
      selector: 'app-external-template',
      templateUrl: './external-template.component.html',
      styleUrls: ['./external-template.component.css']
    })
    export class ExternalTemplateComponent {
      title: string = 'Hello, Angular!';
    }

  • Template File (HTML): external-template.component.html

    <h1>{{ title }}</h1>
    <p>Welcome to the external template example.</p>

  • Styles File (CSS): external-template.component.css

    h1 { color: blue; }

Key Features of Angular Templates:

1. Data Binding:

   • Interpolation: Embedding expressions within double curly braces {{ }} to display data.

     <p>{{ message }}</p>

   • Property Binding: Binding component properties to HTML element attributes using square brackets [].

     <img [src]="imageUrl">

2. Event Binding:

   • Handling user events like clicks, key presses, etc., using parentheses ().

     <button (click)="onClick()">Click me</button>

3. Structural Directives:

   • Directives that alter the DOM layout by adding or removing elements (e.g., *ngIf, *ngFor).

     <div *ngIf="isVisible">Visible content</div>
     <ul>
       <li *ngFor="let item of items">{{ item }}</li>
     </ul>

4. Attribute Directives:

   • Directives that change the appearance or behavior of an element (e.g., ngClass, ngStyle).

     <div [ngClass]="{ 'highlight': isHighlighted }">Highlighted content</div>

Summary:

To define a template in Angular, you can use either an inline template within the @Component decorator or an external template referenced by templateUrl. Templates are written in HTML and can include Angular-specific syntax for data binding, event handling, and using directives. These templates are essential for defining the view and enabling dynamic interactions in Angular applications.