Here are some key points, descriptions, and examples to help improve performance in Angular applications:
1. Use OnPush Change Detection Strategy
Description:
The default change detection strategy checks the whole component tree. OnPush only checks when inputs change or events occur, reducing unnecessary checks.
Example:
@Component({
selector: 'app-user',
changeDetection: ChangeDetectionStrategy.OnPush,
template: `...`
})
2. Lazy Load Feature Modules
Description:
Load modules only when they are needed rather than at the start. This reduces initial load time.
Example:
const routes: Routes = [
{ path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) }
];
3. *Use TrackBy in ngFor
Description:
Improves DOM rendering performance by telling Angular how to track items uniquely.
Example:
<li *ngFor="let user of users; trackBy: trackByUserId">{{ user.name }}</li>
trackByUserId(index: number, user: User) {
return user.id;
}
4. Avoid Memory Leaks with Unsubscriptions
Description:
Always unsubscribe from Observables (e.g., in services, timers, or intervals) to avoid memory leaks.
Example:
ngOnDestroy() {
this.subscription.unsubscribe();
}
5. Use Pure Pipes for Performance
Description:
Pure pipes are only executed when the input data changes, unlike impure pipes which run on every change detection.
Example:
@Pipe({ name: 'capitalize', pure: true })
6. Minimize DOM Manipulation
Description:
Avoid direct DOM manipulation or use Renderer2 if necessary. Keep templates lean and avoid excessive bindings.
7. Use Ahead-of-Time (AOT) Compilation
Description:
AOT compiles Angular HTML and TypeScript code into JavaScript during the build, reducing runtime compilation cost.
Command:
ng build --aot
8. Enable Production Mode
Description:
Angular’s development mode has extra checks and logs. Enabling production mode disables those and enables optimizations.
Example:
import { enableProdMode } from '@angular/core';
if (environment.production) {
enableProdMode();
}
9. Use Web Workers for Heavy Computation
Description:
Offload CPU-heavy work to a Web Worker to keep the UI thread responsive.
10. Optimize Images and Assets
Description:
Use compressed images and preload important assets to reduce loading time.
11. Use Angular Universal for Server-Side Rendering (SSR)
Description:
SSR improves performance for initial load and is beneficial for SEO.
12. Avoid Using any and Use Strong Typing
Description:
Strong typing helps the compiler optimize the code better and catch bugs early.
By applying these tips, you can build faster, more efficient, and more maintainable Angular applications.