Angular Interview Questions

Optimizing the performance of an Angular application involves a combination of best practices, efficient coding techniques, and leveraging Angular’s built-in tools and features. Here are several strategies to optimize Angular application performance:

1. Lazy Loading Modules:

• Purpose: Load feature modules only when needed, reducing the initial load time.
• Implementation:

  const routes: Routes = [
    { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }
  ];

2. Ahead-of-Time (AOT) Compilation:

• Purpose: Compile the application during the build process to improve performance and reduce the size of the JavaScript bundles.
• Implementation:

  ng build --prod --aot

3. Use OnPush Change Detection:

• Purpose: Reduce the number of times Angular checks for changes by using the OnPush change detection strategy.
• Implementation:

  @Component({
    selector: 'app-example',
    templateUrl: './example.component.html',
    changeDetection: ChangeDetectionStrategy.OnPush
  })
  export class ExampleComponent {
    // Component logic
  }

4. Optimize Template Bindings:

• Purpose: Minimize the number of bindings and ensure they are efficient.
• Implementation:
  • Avoid complex expressions in templates.
  • Use trackBy function in ngFor directives.

  <div *ngFor="let item of items; trackBy: trackByFn">{{ item.name }}</div>

5. Preload Lazy Loaded Modules:

• Purpose: Preload lazy-loaded modules in the background to improve user experience.
• Implementation:

  @NgModule({
    imports: [RouterModule.forRoot(routes, { preloadingStrategy: PreloadAllModules })],
    exports: [RouterModule]
  })
  export class AppRoutingModule { }

6. Tree Shaking and Minification:

• Purpose: Remove unused code and minify the JavaScript bundles to reduce the load time.
• Implementation: Automatically handled by Angular CLI during the production build.

  ng build --prod

7. Optimize Images and Assets:

• Purpose: Reduce the size of images and other assets to improve load times.
• Implementation:
  • Use appropriate image formats (e.g., WebP).
  • Compress images.
  • Use lazy loading for images.

8. Use Pure Pipes:

• Purpose: Ensure pipes are executed only when their input data changes.
• Implementation:

  @Pipe({
    name: 'customPipe',
    pure: true
  })
  export class CustomPipe implements PipeTransform {
    transform(value: any): any {
      // Transformation logic
    }
  }

9. Optimize Change Detection:

• Purpose: Manually control change detection to optimize performance.
• Implementation:

  import { ChangeDetectorRef } from '@angular/core';
  
  export class ExampleComponent {
    constructor(private cdr: ChangeDetectorRef) {}
  
    triggerChangeDetection() {
      this.cdr.detectChanges();
    }
  }

10. Server-Side Rendering (SSR):

• Purpose: Improve initial load time and SEO by rendering the application on the server.
• Implementation: Use Angular Universal for SSR.

  ng add @nguniversal/express-engine

11. Use Web Workers:

• Purpose: Offload heavy computations to background threads to keep the UI responsive.
• Implementation:

  // Create a web worker using Angular CLI
  ng generate web-worker my-worker

12. Bundle and Optimize Third-Party Libraries:

• Purpose: Reduce the size of third-party libraries included in the application.
• Implementation: Import only necessary parts of libraries.

  import { specificFunction } from 'large-library';

13. Cache Data and Use Local Storage:

• Purpose: Reduce server requests by caching data locally.
• Implementation: Use services to manage cached data.

  localStorage.setItem('key', JSON.stringify(data));
  const data = JSON.parse(localStorage.getItem('key'));

14. Optimize Forms and Inputs:

• Purpose: Reduce the frequency of change detection for form inputs.
• Implementation: Use debounce time with reactive forms.

  this.myForm.valueChanges.pipe(
    debounceTime(300)
  ).subscribe(value => {
    // Handle form value changes
  });

15. Code Splitting:

• Purpose: Break down large bundles into smaller chunks that can be loaded on demand.
• Implementation: Angular CLI handles this automatically for lazy-loaded modules.

In Summary:

Optimizing the performance of an Angular application involves a combination of techniques, including lazy loading modules, using AOT compilation, implementing OnPush change detection, optimizing template bindings, and using server-side rendering. Additionally, optimizing images, using pure pipes, leveraging web workers, and caching data can significantly enhance performance. Following these strategies ensures that Angular applications are fast, responsive, and scalable.