Angular Performance Optimization Techniques for Faster Loading and Better UX
Tags: webdev, angular
Published: 2023-05-24 19:12:47

## Angular Performance Optimization Techniques for Faster Loading and Better UX



If you are looking to develop high-performing web applications, it’s important to optimize the performance of your Angular application. With Angular, you can build complex applications that deliver a great user experience, but it can also lead to slower load times and reduced performance.

In this article, you’ll learn some Angular performance optimization techniques for faster loading and better user experience. These techniques will help you improve the performance of your Angular app while retaining its rich features.

### 1. Use Ahead-of-Time (AOT) Compilation



Angular offers two modes for compilation: Just-in-Time (JIT) and Ahead-of-Time (AOT). JIT is the default compilation mode, which compiles the application on-the-fly within the user’s browser. This can result in slower load times since the compilation process occurs in real-time. 

On the other hand, AOT compiles the application during the build process, resulting in faster load times, which is beneficial to the overall user experience. Using AOT can reduce the size of your application and increase its performance. 

You can use the Angular CLI to switch to AOT with the following command:

<pre><code>ng build --aot</code></pre>

Or, you can configure the application to use AOT from the beginning by creating a new project with the following command:

<pre><code>ng new my-app --style=scss --prefix=app --routing --skip-tests --skip-git --skip-install --skip-commit --skip-package-json</code></pre>

By default, this command sets the value of the "aot" configuration property in the "angular.json" file to "true".

### 2. Lazy Loading of Modules



When developing Angular applications, it’s important to optimize its loading time. One way to do this is to implement lazy loading of modules. 

In Angular, modules can be loaded on-demand, based on the user’s actions. This means that only the modules that are accessed by the user are loaded, rather than loading the entire application at once.

This technique can improve the initial load time of the application since it loads the minimum amount of code required by the current view. 

Here’s an example of how to use lazy loading of modules in Angular:

<pre><code>const routes: Routes = [
  {
    path: '',
    redirectTo: 'home',
    pathMatch: 'full'
  },
  {
    path: 'home',
    loadChildren: () => import('./home/home.module').then(
      module => module.HomeModule
    )
  },
  {
    path: 'about',
    loadChildren: () => import('./about/about.module').then(
      module => module.AboutModule
    )
  }
];</code></pre>

This code defines three routes, one for the home page, one for the about page, and one for the default route that redirects to the home page. 

The home page and about page is configured to use lazy loading using the "loadChildren" property. "loadChildren" lazy loads the module when the user navigates to the corresponding route. 

### 3. Reduce HTTP requests



HTTP requests are a common cause of slow load times in web applications. Therefore, it’s important to minimize the number of HTTP requests made by the application. 

To reduce HTTP requests, we can use the following techniques:

3.1 Combine HTTP Requests

In Angular, we can combine HTTP requests by using RxJS’s "forkJoin" operator. By combining multiple requests into a single call, we can reduce the time it takes for the application to load.

<pre><code>forkJoin([
  this.http.get('/api/posts'),
  this.http.get('/api/users')
])
.subscribe(results => {
  const posts = results[0];
  const users = results[1];
});</code></pre>

3.2 Use HTTP Caching

HTTP caching allows the client to cache responses from the server, thus reducing the need to make additional HTTP requests. Angular provides a built-in mechanism for HTTP caching, which can be configured in the interceptor:

<pre><code>@Injectable()
export class HttpCacheInterceptor implements HttpInterceptor {
  private cache = new Map<string, HttpResponse<any>>();

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const cachedResponse = this.cache.get(request.url);

    if (cachedResponse) {
      return of(cachedResponse);
    }

    return next.handle(request).pipe(
      tap(event => {
        if (event instanceof HttpResponse) {
          this.cache.set(request.url, event);
        }
      })
    );
  }
}</code></pre>

3.3 Compress Resources

Compressing resources such as images, videos, and stylesheets can reduce the size of the resources, leading to faster load times. 

Angular uses the gzip compression algorithm by default for HTTP responses, which can significantly reduce the payload size of resources being sent to the client. 

### 4. Optimizing Angular Components



Angular components play a crucial role in the performance of your Angular application. By following some best practices, we can make sure that they’re optimized for performance.

4.1 Using TrackBy

When working with lists in Angular, repetitive changes can cause a noticeable hit in performance. To address this, Angular provides a built-in directive called "ngForTrackBy" for the "ngFor" loop, which can optimize the performance of the loop by only updating the items that have actually changed.

<pre><code>trackByFn(index: number, item: any): any {
  return item.id;
}</code></pre>

4.2 Use Immutable Data

Immutable data can improve the performance of Angular applications by reducing the number of changes that need to be made when the state of the application changes. 

To achieve immutability, we can use libraries like Immutable.js or simply create new objects instead of mutating existing ones.

4.3 Use ChangeDetectionStrategy.OnPush

By default, Angular performs change detection on every component each time an event occurs, which can be resource-intensive if your application has complex components. 

To optimize the performance of your application, you can use the "ChangeDetectionStrategy.OnPush" change detection strategy, which only performs change detection when an input property changes.

<pre><code>@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css'],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class MyComponentComponent {
  @Input() data: any;
}</code></pre>

### Conclusion



In this article, we explored several Angular performance optimization techniques that can enhance the performance of your application. By using ahead-of-time compilation, lazy loading of modules, optimizing HTTP requests, and optimizing Angular components, you can build Angular applications that offer a fast and responsive user experience. 

By following these best practices and techniques in your project, you can ensure that your Angular application is optimized for performant, responsive, and efficient delivery.