Angular
Lazy Loading and Change Detection Optimization for Angular Performance
Introduction
Dynamic web applications can be created using Angular, but over time, performance can be raised as a significant issue. Using Lazy Loading and Change Detection Efficiency are two strategies for performance optimization in Angular. In this post, we will take a closer look at these two concepts as important pillars for building high-performance Angular applications.
1. Load Modules When Needed, Not Before: Lazy Loading
In simple words, lazy loading is a concept where feature modules are not included in the initial bundle of the application but are instead loaded on-demand. This basically means that the app will not need to download parts that are not immediately required, although it will cause the time of initial loading to become shorter and the app more responsive.
How to Lazy Load in Angular
Angular by default eagerly loads every module, which will cause a bottleneck in the application. In order to lazy-load any resource:
Create a Feature Module: Organize and divide your application into smaller feature modules.
LoadChildren Routing: Instead of importing feature modules in AppModule, load them dynamically in AppRoutingModule.
Example:
const routes: Routes = [ { path: 'dashboard', loadChildren: () => import('./dashboard/dashboard.module').then(m => m.DashboardModule) },];Benefits of Lazy Loading
- Fast Initial Load: Essential modules will be loaded up front.
- Better Usage Experience: Less time lag for the responsive app perceived by the users.
Efficient Resource Consumption: During the load time, modules load on the need basis consuming less memory.
2. Make Change Detection More Optimized for Performance
About Angular Change Detection
Change detection is basically the push mechanism for Angular which pings at a particular instance and updates whatever has changed at that time stamp in the components and shows directly those in the UI. Without any proper optimization, it leads to possible performance bottlenecks.
Techniques of Change Detection Optimization
a) Use the OnPush Change Detection Strategy
Angular uses by default the Default change detection strategy where all components of a particular component tree get checked against change events. Using the OnPush option can give noticeable performance improvements.
Setting it in the component decorator makes OnPush active:
@Component({ selector: 'app-example', templateUrl: './example.component.html', changeDetection: ChangeDetectionStrategy.OnPush})export class ExampleComponent { @Input() data: any;}
How does OnPush help?
- It updates the component only when the @Input() reference changes.
- It reduces the number of change detection cycles, leading to better performance.
b) Manually Detach and ReAttach Change Detection
In performance-critical components, the ChangeDetectorRef service can be used to take control of change detection.
Example:
constructor(private cd: ChangeDetectorRef) {}ngOnInit() { this.cd.detach(); // Stop automatic change detection}updateComponent() { // Do all updates this.cd.detectChanges(); // Trigger changes manually }
c) Avoid Unnecessary Bindings in Templates
Don′t bind complex expressions in templates directly because they get recomputed during every change detection cycle.
For example, instead of:
<p>{{ users.filter(user => user.active).length }}</p>keep it pre-computed:
activeUsersCount = this.users.filter(user => user.active).length; and bind it in the template:
<p>{{ activeUsersCount }}</p> Conclusion
Lazy Loading and Change Detection Optimization will therefore greatly enhance the loading performance for applications developed in Angular. Initial load time decreases due to lazy loading, whereas cycles of unnecessary rendering are decreased because of change detection efficiency. As such, both provide for a swift, smooth, and efficient user experience.
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