Common Mistakes in Angular and How to Avoid Them

Angular is a powerful framework, but it’s easy to make mistakes, especially if you’re new to it. These mistakes can lead to performance issues, bugs, and maintainability challenges. In this article, we’ll explore some of the most common mistakes developers make when working with Angular and provide practical tips on how to avoid them. By the end of this guide, you’ll have a solid understanding of how to write better Angular code and avoid common pitfalls.

1. Not Using OnPush Change Detection

Mistake: Using the default change detection strategy for all components, which can lead to performance issues in large applications.

Solution: Use the OnPush change detection strategy for components that don’t need frequent updates. This reduces the number of change detection cycles and improves performance.

@Component({
  selector: 'app-example',
  template: `<p>{{ message }}</p>`,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class ExampleComponent {
  @Input() message: string;
}

2. Overusing Two-Way Data Binding

Mistake: Overusing two-way data binding ([(ngModel)]), which can make the application harder to debug and maintain.

Solution: Use one-way data binding ([ngModel]) and event binding ((ngModelChange)) separately to make the data flow more explicit.

<input [ngModel]="name" (ngModelChange)="onNameChange($event)" />

3. Not Unsubscribing from Observables

Mistake: Failing to unsubscribe from observables, which can lead to memory leaks.

Solution: Use the takeUntil operator or the async pipe to automatically unsubscribe from observables.

ngOnDestroy() {
  this.destroy$.next();
  this.destroy$.complete();
}

4. Ignoring Lazy Loading

Mistake: Loading all modules upfront, which increases the initial load time of the application.

Solution: Use lazy loading to load feature modules on demand, improving performance.

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

5. Not Using TrackBy with ngFor

Mistake: Not using trackBy with *ngFor, which can lead to unnecessary DOM updates and performance issues.

Solution: Use the trackBy function to optimize list rendering.

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

6. Poor Error Handling

Mistake: Not handling errors properly, which can lead to unexpected behavior and a poor user experience.

Solution: Use the catchError operator to handle errors in HTTP requests and other asynchronous operations.

this.http.get('https://api.example.com/data').pipe(
  catchError((error) => {
    console.error('Error:', error);
    return throwError(() => new Error('An error occurred.'));
  })
).subscribe();

Conclusion

By avoiding these common mistakes, you can write more efficient, maintainable, and bug-free Angular applications. Whether you’re a beginner or an experienced developer, being aware of these pitfalls and knowing how to avoid them is essential for Angular development.