Angular Interview Practice

What is the role of the ngOnInit lifecycle hook?

1. To trigger change detection

2. To initialize component logic after inputs are set

3. To destroy component resources

4. To manage user inputs

The correct answer is: To initialize component logic after inputs are set

The ngOnInit lifecycle hook is primarily designed for initializing component logic after Angular has set the component's input properties. This is particularly important because when the component is created, it may not have received its input values yet. The ngOnInit method is called right after the Angular initializes the component's data-bound properties, which allows developers to run any initialization logic that depends on those properties. This lifecycle hook is an ideal place to make API calls, set up subscriptions, or perform any setup that requires the input properties to be already established. By utilizing ngOnInit, developers can ensure that their components are fully set up and ready for use with the correct input values when the component is displayed. Other answer choices, while they reflect different functionalities, do not specifically address the purpose of ngOnInit. For instance, triggering change detection is handled by Angular automatically as part of its change detection mechanism, and managing user inputs falls more under the domain of form controls and event handling in components. Destroying component resources pertains to the ngOnDestroy lifecycle hook, which is responsible for cleaning up any resources before the component is destroyed. Thus, option B accurately captures the core responsibility of ngOnInit in the component lifecycle.