Performance Optimization

Performance optimization in Angular applications ensures smooth and fast user experiences. This guide covers various strategies and techniques for optimizing the performance of your Angular applications.

Lazy Loading Modules

Lazy loading modules can significantly reduce the initial load time of your application by loading feature modules only when they are needed:

// app-routing.module.ts
const routes: Routes = [
  { path: '', loadChildren: () => import('./home/home.module').then(m => m.HomeModule) },
  { path: 'about', loadChildren: () => import('./about/about.module').then(m => m.AboutModule) }
];

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

Using OnPush Change Detection

By default, Angular uses the default change detection strategy which checks every component for changes. Using the OnPush strategy can improve performance by only checking components with changed inputs:

// some.component.ts
import { ChangeDetectionStrategy, Component } from '@angular/core';

@Component({
  selector: 'app-some',
  templateUrl: './some.component.html',
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class SomeComponent {
  @Input() data: any;
}

Optimizing Template Expressions

Avoid complex logic in template expressions as it can cause unnecessary re-evaluation. Move complex logic to component methods or properties:

// bad.component.html
{{ someComplexFunction() }}

// good.component.ts
get computedValue() {
  return this.someComplexFunction();
}

Ahead-of-Time (AOT) Compilation

Use AOT compilation to compile your Angular application during the build phase. AOT compilation can improve performance by reducing the amount of JavaScript that needs to be parsed and executed in the browser:

ng build --prod

Tree Shaking

Tree shaking is a technique that removes unused code from the final bundle. Ensure your Angular application is configured to use tree shaking by using AOT compilation and optimizing your imports:

import { Component } from '@angular/core';  // Import only what you need

Lazy Loading Images

Lazy loading images can improve the performance of your application by loading images only when they are in the viewport:

// some.component.html


// Install ng-lazyload-image package
npm install ng-lazyload-image --save

Using Web Workers

Web workers can offload heavy computations to a background thread, freeing up the main thread to improve application performance:

// some.worker.ts
addEventListener('message', ({ data }) => {
  const response = `Worker response to ${data}`;
  postMessage(response);
});

// some.component.ts
if (typeof Worker !== 'undefined') {
  const worker = new Worker(new URL('./some.worker', import.meta.url));
  worker.onmessage = ({ data }) => {
    console.log(`Page got message: ${data}`);
  };
  worker.postMessage('hello');
}

Server-Side Rendering (SSR)

Server-side rendering can improve performance by rendering your Angular application on the server and sending the pre-rendered HTML to the client:

ng add @nguniversal/express-engine

Key Points

Conclusion

Performance optimization is crucial for providing a smooth and fast user experience in your Angular applications. By implementing strategies such as lazy loading, OnPush change detection, optimizing template expressions, AOT compilation, tree shaking, lazy loading images, using web workers, and server-side rendering, you can significantly improve the performance of your applications. Happy coding!