Understanding runOutsideAngular in Angular
In Angular, change detection is crucial for synchronizing the application’s view with the data model. However, automatic change detection can cause performance issues, particularly during heavy computations or when interfacing with external libraries. To optimize performance in such cases, Angular offers the runOutsideAngular method. This blog post explores runOutsideAngular, explains its usage, and provides a sample code example.
What is runOutsideAngular?
The runOutsideAngular method is part of the NgZone service in Angular. It is used to execute a function outside of Angular’s zone, thereby preventing change detection from being triggered. Consequently, it helps in optimizing performance by running certain operations outside the Angular change detection mechanism.
When to Use runOutsideAngular?
Whenever there are long-running tasks, animations, or interactions with non-Angular libraries, runOutsideAngular can be beneficial. By running these tasks outside the Angular zone, unnecessary change detection cycles can be avoided, leading to improved performance.
How to Use runOutsideAngular
Inject the NgZone service into the component first to use runOutsideAngular, then call the method with the function to execute outside Angular’s change detection zone.
Consider a scenario where we need to perform a time-consuming operation without triggering Angular’s change detection.
Step 1: Import and Inject NgZone
import { Component, NgZone } from '@angular/core';
@Component({
selector: 'app-run-outside-angular',
template: `<button (click)="startTask()">Start Task</button>`
})
export class RunOutsideAngularComponent {
constructor(private ngZone: NgZone) {}
startTask() {
this.ngZone.runOutsideAngular(() => {
this.heavyComputation();
});
}
heavyComputation() {
let count = 0;
for (let i = 0; i < 1000000000; i++) {
count += i;
}
console.log('Heavy computation finished:', count);
}
}
Step 2: Use the Component
<app-run-outside-angular></app-run-outside-angular>
In this example, the RunOutsideAngularComponent is defined. First, the NgZone service is imported and injected into the component’s constructor. Next, a method named startTask is created, which calls runOutsideAngular and passes a function to it. This function executes the heavyComputation method, which performs a time-consuming loop operation. As a result, the heavy computation runs without triggering Angular’s change detection.
Conclusion:
In conclusion, runOutsideAngular proves valuable in Angular for optimizing performance by executing specific tasks outside the Angular change detection mechanism. Utilizing this method helps avoid unnecessary change detection cycles, thereby leading to a more efficient application. The provided example illustrates a basic use case, showing how to effectively implement and utilize runOutsideAngular. In complex applications, mastering and leveraging runOutsideAngular can significantly boost performance and responsiveness.