React Hooks Interview Questions & Answers 2026

📖 Introduction

This comprehensive guide focuses on React Hooks interview questions covering modern React development patterns. Whether you're preparing for your first React.js interview or looking to refresh your knowledge, this resource provides detailed answers with code examples to help you succeed.

What you'll learn:

useState Hook: Managing component state in functional components
useEffect Hook: Handling side effects and lifecycle events
useCallback & useMemo: Performance optimization with memoization
useReducer: Complex state management patterns
Custom Hooks: Creating reusable stateful logic
Hook Rules: Understanding the rules of hooks and best practices

Perfect for:

Developers preparing for React.js interviews focusing on hooks
Frontend engineers looking to master modern React patterns
Teams conducting React technical assessments
Anyone learning React Hooks and seeking comprehensive interview preparation

Keywords: React Hooks interview questions, React JS interview questions, React.js interview questions, interview questions on react js Key Features:

10+ React Hooks interview questions with detailed explanations
Code examples for every concept
Updated for 2026 with latest React features
Covers all difficulty levels from beginner to advanced
Practical answers you can use in real interviews

React Hooks

This section focuses on React Hooks interview questions, covering useState, useEffect, useCallback, useMemo, useReducer, and custom hooks. Understanding hooks is crucial for modern React development.

What are the benefits of using hooks in React?
Hooks enable the use of state and other React features in functional components, replacing the need for class components. They streamline code by reducing the reliance on lifecycle methods, enhance readability, and facilitate the reuse of stateful logic across components.
Popular hooks like useState and useEffect are used for managing state and side effects.
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What are the rules of React hooks?
React hooks should be called at the top level of a function, not inside loops, conditions, or nested functions. They must only be used within React function components or custom hooks. These guidelines ensure proper state management and lifecycle behavior.
Key rules:
1. Only call hooks at the top level: Don't call hooks inside loops, conditions, or nested functions
2. Only call hooks from React functions: Call hooks from React function components or custom hooks
3. Custom hooks must start with 'use': This naming convention helps React identify hooks
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What is the difference between useEffect and useLayoutEffect in React?
useEffect and useLayoutEffect both handle side effects in React functional components but differ in when they run:
- useEffect runs asynchronously after the DOM has rendered, making it suitable for tasks like data fetching or subscriptions.
- useLayoutEffect runs synchronously after DOM updates but before the browser paints, ideal for tasks like measuring DOM elements or aligning the UI with the DOM.
```
import React, { useEffect, useLayoutEffect, useRef } from "react"

function Example() {
  const ref = useRef()

  useEffect(() => {
    console.log("useEffect: Runs after DOM paint")
  })

  useLayoutEffect(() => {
    console.log("useLayoutEffect: Runs before DOM paint")
    console.log("Element width:", ref.current.offsetWidth)
  })

  return <div ref={ref}>Hello</div>
}
```
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What does the dependency array of useEffect affect?
The dependency array of useEffect controls when the effect re-runs:
- If it's empty [], the effect runs only once after the initial render.
- If it contains variables [dep1, dep2], the effect re-runs whenever any of those variables change.
- If omitted, the effect runs after every render.
```
useEffect(() => {
  // Runs on every render
})

useEffect(() => {
  // Runs only once on mount
}, [])

useEffect(() => {
  // Runs when count or name changes
}, [count, name])
```
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What is the useRef hook in React and when should it be used?
The useRef hook creates a mutable object that persists through renders, allowing direct access to DOM elements, storing mutable values without causing re-renders, and maintaining references to values.
For instance, useRef can be utilized to focus on an input element:
```
import React, { useRef, useEffect } from "react"

function TextInputWithFocusButton() {
  const inputEl = useRef(null)
  useEffect(() => {
    inputEl.current.focus()
  }, [])
  return <input ref={inputEl} type="text" />
}
```
Common use cases:
- Accessing DOM elements directly
- Storing mutable values that don't trigger re-renders
- Keeping references to previous values
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What is the useCallback hook in React and when should it be used?
The useCallback hook memoizes functions to prevent their recreation on every render. This is especially beneficial when passing callbacks to optimized child components that depend on reference equality to avoid unnecessary renders.
```
const memoizedCallback = useCallback(() => {
  doSomething(a, b)
}, [a, b])
```
When to use:
- When passing callbacks to child components wrapped in React.memo
- When callbacks are dependencies of other hooks
- To prevent unnecessary re-renders of child components
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What is the useMemo hook in React and when should it be used?
The useMemo hook memoizes costly calculations, recomputing them only when dependencies change. This enhances performance by avoiding unnecessary recalculations.
```
const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b])
```
When to use:
- For expensive computations that don't need to run on every render
- When passing computed values to child components to prevent unnecessary re-renders
- To optimize performance in components with heavy calculations
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What is the useReducer hook in React and when should it be used?
The useReducer hook manages complex state logic in functional components, serving as an alternative to useState. It's ideal when state has multiple fields or when the next state relies on the previous one.
The useReducer hook accepts a reducer function and an initial state. The reducer function is passed the current state and action and returns a new state.
```
const [state, dispatch] = useReducer(reducer, initialState)

// Example usage:
dispatch({ type: "increment" })
```
When to use:
- Complex state logic with multiple sub-values
- When next state depends on previous state
- When you want centralized state management in a component
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What is the useId hook in React and when should it be used?
The useId hook generates unique IDs for elements within a component, which is crucial for accessibility by dynamically creating ids that can be used for linking form inputs and labels. It guarantees unique IDs across the application even if the component renders multiple times.
```
import { useId } from "react"

function MyComponent() {
  const id = useId()

  return (
    <div>
      <label htmlFor={id}>Name:</label>
      <input id={id} type="text" />
    </div>
  )
}
```
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Can you explain how to create and use custom hooks in React?

To create and use custom hooks in React:

Create a function that starts with use and uses built-in hooks like useState or useEffect
Return the values or functions you want to share.

Example:

function useForm(initialState) {
  const [formData, setFormData] = useState(initialState);
  const handleChange = (e) =>
    setFormData({ ...formData, [e.target.name]: e.target.value });
  return [formData, handleChange];
}

Use the Hook:

function MyForm() {
  const [formData, handleChange] = useForm({ name: '', email: '' });
  return <input name="name" value={formData.name} onChange={handleChange} />;
}