FAQs on React JS In Urdu ~ React Component Lifecycle Events (Part 6 of 6)

Question 1

1. What are React component lifecycle events?

Accepted Answer

Ans. React component lifecycle events are methods that are automatically called at different stages of a component's life cycle. These events allow developers to perform specific actions at different points in the rendering process, such as initialization, rendering, updating, and unmounting.

Question 2

2. How many lifecycle events are there in React?

Accepted Answer

Ans. In React, there are three main phases of a component's lifecycle: Mounting, Updating, and Unmounting. Each phase has specific lifecycle events associated with it. The Mounting phase includes events like constructor, render, componentDidMount, etc. The Updating phase includes events like shouldComponentUpdate, render, componentDidUpdate, etc. The Unmounting phase includes the componentWillUnmount event.

Question 3

3. What is the purpose of componentDidMount in React?

Accepted Answer

Ans. componentDidMount is a React lifecycle event that is called immediately after a component is mounted or inserted into the DOM. This event is commonly used for tasks that require interaction with the DOM or external data fetching, such as initializing third-party libraries, fetching data from an API, or setting up event listeners.

Question 4

4. How is shouldComponentUpdate used in React?

Accepted Answer

Ans. shouldComponentUpdate is a React lifecycle event that allows developers to control whether a component should re-render or not. By default, React will re-render a component whenever its state or props change. However, by implementing shouldComponentUpdate, developers can optimize performance by preventing unnecessary re-renders. This method takes the next props and state as arguments and returns a boolean value indicating whether the component should update or not.

Question 5

5. When is componentWillUnmount called in React?

Accepted Answer

Ans. componentWillUnmount is a React lifecycle event that is called immediately before a component is unmounted or removed from the DOM. This event is commonly used for cleanup tasks, such as canceling timers, removing event listeners, or clearing any subscriptions or resources that were set up in the componentDidMount lifecycle event. It is important to perform these cleanup tasks to avoid memory leaks and ensure the component is properly unmounted.

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