Thursday 15 February 2024

What are Lifecycle Hooks in Angular? 040

 What are Lifecycle Hooks in Angular?

Lifecycle hooks in Angular are like milestones in the journey of a component: specific points where Angular calls predefined methods on a component instance throughout its creation, change detection, and destruction. These hooks provide you with opportunities to react to key moments in the component's lifecycle and execute necessary logic at the most appropriate times.

Here's a breakdown of the key lifecycle hooks in Angular:

1. Creation Hooks:

  • ngOnChanges: Called whenever input properties bound to the component change. Use this to react to data changes and update the component's state accordingly.

  • ngOnInit: Called after the component has been initialized and its inputs have been set. This is a common place to perform initial setup tasks, fetch data, or subscribe to events.

  • ngDoCheck: Called during every change detection cycle, allowing you to manually detect changes not caught by Angular's default mechanism. Use it cautiously for performance reasons.

2. Change Detection Hooks:

  • ngAfterContentInit: Called after the component's projected content (content from other child components) has been checked. Use this to access or manipulate projected content if needed.

  • ngAfterViewInit: Called after the component's view (template) has been initialized and rendered. This is a good place to interact with DOM elements directly, access child components using ViewChild, or subscribe to DOM events.

3. Destruction Hook:

  • ngOnDestroy: Called just before the component is destroyed. Use this to clean up resources, unsubscribe from subscriptions, or perform any necessary teardown tasks.

Why Use Lifecycle Hooks?

Effectively using lifecycle hooks offers several benefits:

  • Organized Code: Hooks keep your component logic structured and focused on specific stages, improving readability and maintainability.

  • Data Fetching: You can fetch data or interact with APIs at appropriate moments in the lifecycle, ensuring data is available when needed.

  • Side Effect Management: Hooks like ngOnDestroy help you prevent memory leaks and unexpected behavior by cleaning up resources responsibly.

  • Testing: By understanding when specific hooks are called, you can create more targeted and effective tests for your components.


  • Choose the appropriate hook based on the action you need to perform.

  • Avoid overuse of ngDoCheck due to its potential performance impact.

  • Utilize hooks judiciously to maintain clean and well-structured components.

By understanding and leveraging lifecycle hooks effectively, you can build dynamic and well-managed Angular components that react appropriately to various stages of their existence. Feel free to ask if you have any further questions or specific use cases for lifecycle hooks!

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