Change Detection Strategies in Angular

Introduction

Change detection is a core feature of Angular that enables the framework to check for changes in the application state and update the view accordingly. Understanding change detection strategies is essential for optimizing performance and enhancing user experience.

What is Change Detection?

Change detection in Angular is the mechanism that allows the framework to respond to changes in application state. It involves checking the component's state and determining if the view needs to be updated.

Change Detection Mechanism

• Angular maintains a tree of components.
• Each component has a corresponding view that displays its data.
• When data changes, Angular checks the components for updates.

Change Detection Strategies

Angular provides two primary change detection strategies:

1. Default Strategy

The default change detection strategy is used unless specified otherwise. It checks all components in the application during each change detection cycle.

@Component({
  selector: 'app-example',
  template: `
{{ title }}
`,
})
export class ExampleComponent {
  title = 'Default Change Detection';
}
            

2. OnPush Strategy

The OnPush strategy optimizes performance by only checking the component when any of its input properties change or an event occurs within the component.

@Component({
  selector: 'app-example-onpush',
  template: `
{{ title }}
`,
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class ExampleOnPushComponent {
  @Input() title: string;
}
            

Best Practices

Optimizing Change Detection

• Use the OnPush change detection strategy for performance-critical components.
• Limit the number of bindings in templates to reduce the check frequency.
• Detach change detection for heavy components that do not change often using the ChangeDetectorRef.

FAQ