This section focuses on Angular performance optimization concepts, answering key questions with detailed explanations, examples, and steps to implement.
1. What are some ways to optimize Angular applications?
Answer:
Angular applications can be optimized using techniques like:
- Using Ahead-of-Time (AOT) compilation.
- Lazy loading modules.
- OnPush change detection strategy.
- Using trackBy with *ngFor.
- Minifying and compressing assets.
Example:
// app-routing.module.ts
const routes: Routes = [
{ path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) },
];
Steps to Implement:
- Enable AOT compilation in
angular.json. - Use lazy loading for feature modules.
- Replace
ChangeDetectionStrategy.DefaultwithChangeDetectionStrategy.OnPush. - Use
trackBywith *ngFor to improve rendering.
2. How does change detection work in Angular?
Answer:
Change detection checks the component tree for updates and synchronizes the view with the model.
Steps:
- Angular creates a component tree.
- Each component’s state is compared with the previous state.
- Angular updates the DOM where changes are detected.
Example:
@Component({
selector: 'app-test',
template: '<p>{{data}}</p>',
changeDetection: ChangeDetectionStrategy.OnPush
})
export class TestComponent {
@Input() data: string;
}
3. What is the OnPush change detection strategy?
Answer:
OnPush skips checking a component’s subtree unless its @Input properties change or events occur.
Steps to Implement:
- Add
ChangeDetectionStrategy.OnPushin the component decorator. - Use immutable objects for input properties.
4. How do you lazy load components?
Answer:
Lazy loading defers loading components or modules until they are needed.
Steps to Implement:
- Use Angular CLI to generate a module.
- Configure routes with
loadChildren.
5. What is preloading in Angular? How is it used?
Answer:
Preloading loads lazy-loaded modules in the background after the application is bootstrapped.
6. How do you optimize Angular templates?
Answer:
Optimize templates by:
- Minimizing the use of complex expressions.
- Using trackBy for *ngFor.
7. What are Angular zones, and how do they work?
Answer:
Zones handle asynchronous operations and trigger change detection automatically.
8. How do you reduce bundle size in Angular?
Answer:
Reduce bundle size by:
- Using tree-shakable libraries.
- Lazy loading modules.
9. How do you debug performance issues in Angular?
Answer:
Use tools like Angular DevTools, Chrome DevTools, and Lighthouse for profiling and debugging.
10. How does Ahead-of-Time (AOT) compilation improve performance?
Answer:
AOT pre-compiles templates during the build phase, reducing runtime overhead.
11. How do you use trackBy with ngFor?
Answer:
Use trackBy to improve rendering performance by uniquely identifying items in a list.
12. What is server-side rendering (SSR) in Angular?
Answer:
SSR pre-renders Angular applications on the server, improving load time and SEO.
13. How does ChangeDetectorRef work in Angular?
Answer:
ChangeDetectorRef allows manual control over change detection.
14. What is differential loading?
Answer:
Differential loading generates multiple bundles for modern and legacy browsers.
15. How do you optimize third-party libraries in Angular?
Answer:
Import only required modules and functions to minimize the bundle size.
16. What is the role of Web Workers in Angular?
Answer:
Web Workers offload computationally expensive tasks to a background thread.
17. How do you handle large lists in Angular?
Answer:
Use virtual scrolling to render only visible items.
18. What is the impact of using large third-party libraries?
Answer:
Large libraries increase the bundle size and affect load time. Optimize by tree-shaking.
19. How does lazy loading images improve performance?
Answer:
Lazy loading defers image loading until they are visible in the viewport.
20. How do you measure Angular application performance?
Answer:
Use Angular DevTools and browser profiling tools to measure performance metrics.