100 React JS questions

Set 4: Super Hard / Expert Level (with Answers) 1. What are the phases of the React component lifecycle?👉 For class components: Mounting (constructor → render → componentDidMount) Updating (shouldComponentUpdate.

Set 3: Hard (Advanced Level) 1. What is reconciliation in React?👉 Reconciliation is the process where React compares the new virtual DOM with the previous one and updates only the.

🟡 Set 2: Medium (A Little Harder) 1. What are controlled and uncontrolled components?👉 Controlled components are form elements whose values are controlled by React state.👉 Uncontrolled components manage their.

🟢 Set 1: Very Simple (Beginner) Questions and Answers 1. What is React JS?👉 React JS is a JavaScript library used for building user interfaces, especially single-page applications. 2. What.