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10 Best Practices for Optimizing Angular Performance


This content originally appeared on DEV Community and was authored by Dipak Ahirav

Optimizing the performance of your Angular application is crucial for providing a smooth user experience. Here are 10 best practices to help you get the most out of your Angular apps.

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1. OnPush Change Detection Strategy 🧠

By default, Angular uses the Default change detection strategy, which checks all components for changes. Using the OnPush strategy reduces the number of checks by only checking components when their inputs change.

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

2. Use TrackBy with ngFor 🔄

Using trackBy in ngFor helps Angular identify items in a list, reducing the number of DOM manipulations.

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

trackByFn(index, item) {
  return item.id;
}

3. Lazy Loading Modules 📦

Lazy loading modules ensures that only the necessary parts of your application are loaded, reducing the initial load time.

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

4. Optimize Template Expressions 🖋

Avoid complex calculations and function calls in template expressions. Instead, compute values in the component class and bind them to the template.

<!-- Instead of this -->
<div>{{ computeHeavyTask() }}</div>

<!-- Use this -->
<div>{{ computedValue }}</div>

ngOnInit() {
  this.computedValue = this.computeHeavyTask();
}

5. Use AOT Compilation 🛠

Ahead-of-Time (AOT) compilation pre-compiles your Angular templates and components, resulting in faster rendering and smaller bundle sizes.

ng build --prod --aot

6. Optimize Styles and Scripts Loading 🎨

Load styles and scripts conditionally to reduce the initial load. Use ngStyle and ngClass for conditional styling.

<div [ngClass]="{'class-a': conditionA, 'class-b': conditionB}"></div>

7. Use Pure Pipes for Data Transformation 📊

Pure pipes are stateless and only recalculate when their input arguments change, making them more efficient than impure pipes.

@Pipe({ name: 'purePipe', pure: true })
export class PurePipe implements PipeTransform {
  transform(value: any, ...args: any[]): any {
    // Transformation logic
  }
}

8. Minimize the Use of Third-Party Libraries 📚

Only include necessary third-party libraries and remove unused ones. This reduces the bundle size and improves load times.

npm prune

9. Optimize Images and Assets 🖼

Use optimized images and lazy load them to improve performance. Tools like ImageOptim or online services can help reduce image sizes.

<img [src]="imageSrc" loading="lazy" />

10. Avoid Memory Leaks 🧹

Unsubscribe from Observables and detach event listeners to prevent memory leaks.

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html'
})
export class MyComponent implements OnDestroy {
  private subscription: Subscription;

  ngOnInit() {
    this.subscription = this.myService.getData().subscribe();
  }

  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
}

By following these best practices, you can optimize the performance of your Angular applications, providing a better experience for your users. Happy coding! 🚀

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This content originally appeared on DEV Community and was authored by Dipak Ahirav