Optimizing Angular Application Performance with Change Detection Strategy

Being proficient in the Change Detection mechanism is pivotal to developing efficient Angular applications. One strategic method to optimize an Angular application's performance is by setting the Change Detection Strategy to OnPush.

What is OnPush Strategy?

The Change Detection strategy in Angular aids in controlling when our component should re-render. When the Change Detection Strategy is set to OnPush, the Angular application only checks or refreshes the component when there is a change in @Input()properties, or when an event is originated from the component itself. This enhances the application's performance as it prevents unnecessary re-rendering of components that have no alterations, offering a much smoother and faster user experience.

Practical Example

For instance, consider a situation where you have a parent component and multiple child components under it. If the Change Detection Strategy is set to Default, Angular would constantly check for changes in each component, causing needless performance overhead.

@Component({
  selector: 'app-parent',
  changeDetection: ChangeDetectionStrategy.Default,
  template: `<app-child></app-child>`
})

However, if you adjust the Change Detection Strategy to OnPush, Angular will only wake up when there's a shift in the @Input() properties or when an event from the component occurs. This is how to set it up:

@Component({
  selector: 'app-child',
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `<div></div>`
})

With this strategy, the child components will only be checked when there's an actual change, thereby improving the application's efficiency immensely.

Key Insights and Best Practices

While the OnPush strategy significantly optimizes application performance, it must be noted that this approach is not a silver bullet. Incorrect usage can lead to unexpected behavior and bugs that are difficult to trace. Therefore, it is paramount to understand when it's appropriate to use it.

For instance, OnPush works best with immutable data. Anytime you change an input property, make sure to give a new reference; otherwise, Angular's Change Detection won't recognize the alteration.

In sum, using the OnPush strategy for Change Detection in Angular has valuable benefits: it reduces unnecessary checks, leading to a faster, more efficient application. Nonetheless, always consider your app's needs to decide the optimal strategy.