NgZone in Angular | Angular's NgZone for Efficient Change Detection | runOutsideAngular function

In Angular, NgZone is a service provided by the Angular framework to manage and facilitate change detection. Angular's change detection mechanism is a crucial part of its reactive architecture, where the framework monitors and updates the UI whenever the application's data model changes.

NgZone helps Angular detect changes efficiently by running certain code outside or inside of Angular's zone. The zone is a concept borrowed from Zone.js, a library used by Angular to intercept asynchronous operations like setTimeout, XMLHttpRequest, etc., and trigger Angular's change detection mechanism accordingly.

Here's how NgZone works:

Inside the Zone: Code executed within Angular's zone is considered "inside" the zone. Angular automatically triggers change detection after any asynchronous operation that originates from inside the zone (e.g., events, promises, timers, etc.).
Outside the Zone: Code executed outside Angular's zone is considered "outside" the zone. Angular does not automatically trigger change detection after any asynchronous operation that originates from outside the zone.

NgZone provides methods like run(), runGuarded(), and onStable() to control change detection behavior. Developers can use NgZone it to explicitly run code inside or outside Angular's zone as needed. This can be particularly useful for optimizing performance, handling third-party libraries that don't trigger Angular's change detection, or dealing with long-running tasks that could potentially block the UI.

Here's a basic example:

import { Component, NgZone } from '@angular/core';

@Component({
  selector: 'app-component',
  template: `
    <button (click)="runOutsideZone()">Run outside zone</button>
  `
})
export class appComponent {
  constructor(private ngZone: NgZone) {}

  runOutsideZone() {
    this.ngZone.runOutsideAngular(() => {
      setTimeout(() => {
        // This code runs outside Angular's zone
        // Angular won't automatically trigger change detection after this timeout
        console.log('Outside zone');
      }, 1000);
    });
  }
}