React is an open source JavaScript library for building awesome and complex user interfaces and is one of the most popular in the JavaScript ecosystem.
TLDR ?
React hooks are functions that allow you to use React state and other features within functional components, enabling tasks like handling side effects and accessing context without writing complex React classes. Using React hooks also enhances code readability and maintainability for developers.
In this article, I will share a list of the 38 React.js hooks and their use cases, which can be considered one of the best resources for React and JavaScript developers.
1. useState
Manages local component state.
import { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
<div>
<button onClick={() => setCount(count + 1)}>Increment</button>
<p>Count: {count}</p>
</div>
);
}
2. useEffect
Performs side effects in function components.
import { useEffect, useState } from 'react';
function DataFetcher() {
const [data, setData] = useState(null);
useEffect(() => {
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => setData(data));
}, []);
return <div>Data: {data ? JSON.stringify(data) : 'Loading...'}</div>;
}
3. useContext
Consumes context in a component.
import { useContext } from 'react';
import { ThemeContext } from './ThemeContext';
function ThemedButton() {
const theme = useContext(ThemeContext);
return <button style={{ background: theme.background }}>Click me</button>;
}
4.useReducer
Manages complex state logic
import { useReducer } from 'react';
const initialState = { count: 0 };
function reducer(state, action) {
switch (action.type) {
case 'increment':
return { count: state.count + 1 };
case 'decrement':
return { count: state.count - 1 };
default:
throw new Error();
}
}
function Counter() {
const [state, dispatch] = useReducer(reducer, initialState);
return (
<div>
<button onClick={() => dispatch({ type: 'decrement' })}>-</button>
<span>{state.count}</span>
<button onClick={() => dispatch({ type: 'increment' })}>+</button>
</div>
);
}
5. useCallback
Returns a memoized callback function.
import { useCallback, useState } from 'react';
function CallbackComponent() {
const [count, setCount] = useState(0);
const increment = useCallback(() => {
setCount(count + 1);
}, [count]);
return <button onClick={increment}>Count: {count}</button>;
}
6. useMemo
Memoizes expensive calculations i.e stores results of resource-intensive calculations for future use.
import { useMemo, useState } from 'react';
function Fibonacci() {
const [num, setNum] = useState(1);
const fib = useMemo(() => {
const computeFib = (n) => (n <= 1 ? n : computeFib(n - 1) + computeFib(n - 2));
return computeFib(num);
}, [num]);
return (
<div>
<button onClick={() => setNum(num + 1)}>Next Fibonacci</button>
<p>Fibonacci of {num} is {fib}</p>
</div>
);
}
7.useRef
Accesses DOM elements or stores mutable values.
import { useRef } from 'react';
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
inputEl.current.focus();
};
return (
<div>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</div>
);
}
8.useImperativeHandle
Customizes the instance value exposed by a ref.
import { forwardRef, useImperativeHandle, useRef } from 'react';
const FancyInput = forwardRef((props, ref) => {
const inputRef = useRef();
useImperativeHandle(ref, () => ({
focus: () => {
inputRef.current.focus();
},
}));
return <input ref={inputRef} />;
});
function App() {
const fancyInputRef = useRef();
return (
<div>
<FancyInput ref={fancyInputRef} />
<button onClick={() => fancyInputRef.current.focus()}>Focus input</button>
</div>
);
}
9. useLayoutEffect
Synchronizes with the DOM layout.
import { useEffect, useLayoutEffect, useRef, useState } from 'react';
function MeasureWidth() {
const ref = useRef();
const [width, setWidth] = useState(0);
useLayoutEffect(() => {
setWidth(ref.current.offsetWidth);
}, []);
return (
<div>
<div ref={ref} style={{ width: '50%' }}>
Resize the window to see the effect.
</div>
<p>Width: {width}px</p>
</div>
);
}
10.useDebugValue
Displays custom label in React DevTools.
import { useDebugValue, useState } from 'react';
function useFriendStatus(friendID) {
const [isOnline, setIsOnline] = useState(null);
useDebugValue(isOnline ? 'Online' : 'Offline');
// Simulate an asynchronous operation
setTimeout(() => setIsOnline(Math.random() > 0.5), 1000);
return isOnline;
}
function FriendStatus({ friendID }) {
const isOnline = useFriendStatus(friendID);
if (isOnline === null) {
return 'Loading...';
}
return isOnline ? 'Online' : 'Offline';
}
11.useFetch
Fetches data from an API.
import { useEffect, useState } from 'react';
function useFetch(url) {
const [data, setData] = useState(null);
const [loading, setLoading] = useState(true);
useEffect(() => {
fetch(url)
.then(response => response.json())
.then(data => {
setData(data);
setLoading(false);
});
}, [url]);
return { data, loading };
}
function App() {
const { data, loading } = useFetch('https://jsonplaceholder.typicode.com/posts');
if (loading) {
return <p>Loading...</p>;
}
return (
<ul>
{data.map(post => (
<li key={post.id}>{post.title}</li>
))}
</ul>
);
}
12.useLocalStorage
Manages state with local storage.
import { useState } from 'react';
function useLocalStorage(key, initialValue) {
const [storedValue, setStoredValue] = useState(() => {
try {
const item = window.localStorage.getItem(key);
return item ? JSON.parse(item) : initialValue;
} catch (error) {
console.error(error);
return initialValue;
}
});
const setValue = (value) => {
try {
const valueToStore = value instanceof Function ? value(storedValue) : value;
setStoredValue(valueToStore);
window.localStorage.setItem(key, JSON.stringify(valueToStore));
} catch (error) {
console.error(error);
}
};
return [storedValue, setValue];
}
function App() {
const [name, setName] = useLocalStorage('name', 'Bob');
return (
<div>
<input value={name} onChange={(e) => setName(e.target.value)} />
<p>Hello, {name}!</p>
</div>
);
}
13. useDebounce
Debounces a value over time.
import { useEffect, useState } from 'react';
function useDebounce(value, delay) {
const [debouncedValue, setDebouncedValue] = useState(value);
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value);
}, delay);
return () => {
clearTimeout(handler);
};
}, [value, delay]);
return debouncedValue;
}
function App() {
const [text, setText] = useState('');
const debouncedText = useDebounce(text, 500);
return (
<div>
<input value={text} onChange={(e) => setText(e.target.value)} />
<p>Debounced Value: {debouncedText}</p>
</div>
);
}
14.usePrevious
Stores the previous value of a variable.
import { useEffect, useRef } from 'react';
function usePrevious(value) {
const ref = useRef();
useEffect(() => {
ref.current = value;
}, [value]);
return ref.current;
}
function App() {
const [count, setCount] = useState(0);
const previousCount = usePrevious(count);
return (
<div>
<button onClick={() => setCount(count + 1)}>Count: {count}</button>
<p>Previous Count: {previousCount}</p>
</div>
);
}
15. useWindowSize
Tracks window size.
import { useEffect, useState } from 'react';
function useWindowSize() {
const [size, setSize] = useState({ width: window.innerWidth, height: window.innerHeight });
useEffect(() => {
const handleResize = () => {
setSize({ width: window.innerWidth, height: window.innerHeight });
};
window.addEventListener('resize', handleResize);
return () => window.removeEventListener('resize', handleResize);
}, []);
return size;
}
function App() {
const { width, height } = useWindowSize();
return (
<div>
<p>Width: {width}px</p>
<p>Height: {height}px</p>
</div>
);
}
16.useHover
Detects if an element is hovered.
import { useCallback, useState } from 'react';
function useHover() {
const [hovered, setHovered] = useState(false);
const onMouseOver = useCallback(() => setHovered(true), []);
const onMouseOut = useCallback(() => setHovered(false), []);
return { hovered, onMouseOver, onMouseOut };
}
function HoverComponent() {
const { hovered, onMouseOver, onMouseOut } = useHover();
return (
<div onMouseOver={onMouseOver} onMouseOut={onMouseOut}>
{hovered ? 'Hovering' : 'Not Hovering'}
</div>
);
}
17. useOnlineStatus
Tracks online status.
import { useEffect, useState } from 'react';
function useOnlineStatus() {
const [isOnline, setIsOnline] = useState(navigator.onLine);
useEffect(() => {
const handleOnline = () => setIsOnline(true);
const handleOffline = () => setIsOnline(false);
window.addEventListener('online', handleOnline);
window.addEventListener('offline', handleOffline);
return () => {
window.removeEventListener('online', handleOnline);
window.removeEventListener('offline', handleOffline);
};
}, []);
return isOnline;
}
function App() {
const isOnline = useOnlineStatus();
return <div>{isOnline ? 'Online' : 'Offline'}</div>;
}
18. useEventListener
Attaches an event listener.
import { useEffect, useRef } from 'react';
function useEventListener(eventName, handler, element = window) {
const savedHandler = useRef();
useEffect(() => {
savedHandler.current = handler;
}, [handler]);
useEffect(() => {
const eventListener = (event) => savedHandler.current(event);
element.addEventListener(eventName, eventListener);
return () => {
element.removeEventListener(eventName, eventListener);
};
}, [eventName, element]);
}
function App() {
useEventListener('click', () => alert('Window clicked!'));
return <div>Click anywhere!</div>;
}
19.useInterval
Sets up an interval with a dynamic delay.
import { useEffect, useRef } from 'react';
function useInterval(callback, delay) {
const savedCallback = useRef();
useEffect(() => {
savedCallback.current = callback;
}, [callback]);
useEffect(() => {
function tick() {
savedCallback.current();
}
if (delay !== null) {
const id = setInterval(tick, delay);
return () => clearInterval(id);
}
}, [delay]);
}
function Timer() {
const [count, setCount] = useState(0);
useInterval(() => setCount(count + 1), 1000);
return <div>Count: {count}</div>;
}
20. useTimeout
Sets up a timeout.
import { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
<div>
<button onClick={() => setCount(count + 1)}>Increment</button>
<p>Count: {count}</p>
</div>
);
}
21. useOnClickOutside
Detects clicks outside a component.
import { useEffect, useState } from 'react';
function DataFetcher() {
const [data, setData] = useState(null);
useEffect(() => {
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => setData(data));
}, []);
return <div>Data: {data ? JSON.stringify(data) : 'Loading...'}</div>;
}
22. useClipboard
Handles clipboard operations.
import { useContext } from 'react';
import { ThemeContext } from './ThemeContext';
function ThemedButton() {
const theme = useContext(ThemeContext);
return <button style={{ background: theme.background }}>Click me</button>;
}
23. useDarkMode
Manages dark mode preference.
import { useReducer } from 'react';
const initialState = { count: 0 };
function reducer(state, action) {
switch (action.type) {
case 'increment':
return { count: state.count + 1 };
case 'decrement':
return { count: state.count - 1 };
default:
throw new Error();
}
}
function Counter() {
const [state, dispatch] = useReducer(reducer, initialState);
return (
<div>
<button onClick={() => dispatch({ type: 'decrement' })}>-</button>
<span>{state.count}</span>
<button onClick={() => dispatch({ type: 'increment' })}>+</button>
</div>
);
}
24.useToggle
Toggles between boolean values.
import { useCallback, useState } from 'react';
function CallbackComponent() {
const [count, setCount] = useState(0);
const increment = useCallback(() => {
setCount(count + 1);
}, [count]);
return <button onClick={increment}>Count: {count}</button>;
}
25. useTheme
Toggles between light and dark themes.
import { useMemo, useState } from 'react';
function Fibonacci() {
const [num, setNum] = useState(1);
const fib = useMemo(() => {
const computeFib = (n) => (n <= 1 ? n : computeFib(n - 1) + computeFib(n - 2));
return computeFib(num);
}, [num]);
return (
<div>
<button onClick={() => setNum(num + 1)}>Next Fibonacci</button>
<p>Fibonacci of {num} is {fib}</p>
</div>
);
}
26. useMedia
Queries media properties.
import { useRef } from 'react';
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
inputEl.current.focus();
};
return (
<div>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</div>
);
}
27. useLockBodyScroll
Locks the body scroll.
import { forwardRef, useImperativeHandle, useRef } from 'react';
const FancyInput = forwardRef((props, ref) => {
const inputRef = useRef();
useImperativeHandle(ref, () => ({
focus: () => {
inputRef.current.focus();
},
}));
return <input ref={inputRef} />;
});
function App() {
const fancyInputRef = useRef();
return (
<div>
<FancyInput ref={fancyInputRef} />
<button onClick={() => fancyInputRef.current.focus()}>Focus input</button>
</div>
);
}
28.useKeyPress
Detects key press.
import { useEffect, useLayoutEffect, useRef, useState } from 'react';
function MeasureWidth() {
const ref = useRef();
const [width, setWidth] = useState(0);
useLayoutEffect(() => {
setWidth(ref.current.offsetWidth);
}, []);
return (
<div>
<div ref={ref} style={{ width: '50%' }}>
Resize the window to see the effect.
</div>
<p>Width: {width}px</p>
</div>
);
}
29. useDocumentTitle
Updates document title.
import { useDebugValue, useState } from 'react';
function useFriendStatus(friendID) {
const [isOnline, setIsOnline] = useState(null);
useDebugValue(isOnline ? 'Online' : 'Offline');
// Simulate an asynchronous operation
setTimeout(() => setIsOnline(Math.random() > 0.5), 1000);
return isOnline;
}
function FriendStatus({ friendID }) {
const isOnline = useFriendStatus(friendID);
if (isOnline === null) {
return 'Loading...';
}
return isOnline ? 'Online' : 'Offline';
}
30. useHover
Handles hover state.
import { useEffect, useState } from 'react';
function useFetch(url) {
const [data, setData] = useState(null);
const [loading, setLoading] = useState(true);
useEffect(() => {
fetch(url)
.then(response => response.json())
.then(data => {
setData(data);
setLoading(false);
});
}, [url]);
return { data, loading };
}
function App() {
const { data, loading } = useFetch('https://jsonplaceholder.typicode.com/posts');
if (loading) {
return <p>Loading...</p>;
}
return (
<ul>
{data.map(post => (
<li key={post.id}>{post.title}</li>
))}
</ul>
);
}
31.useGeolocation
Retrieves geolocation.
import { useState } from 'react';
function useLocalStorage(key, initialValue) {
const [storedValue, setStoredValue] = useState(() => {
try {
const item = window.localStorage.getItem(key);
return item ? JSON.parse(item) : initialValue;
} catch (error) {
console.error(error);
return initialValue;
}
});
const setValue = (value) => {
try {
const valueToStore = value instanceof Function ? value(storedValue) : value;
setStoredValue(valueToStore);
window.localStorage.setItem(key, JSON.stringify(valueToStore));
} catch (error) {
console.error(error);
}
};
return [storedValue, setValue];
}
function App() {
const [name, setName] = useLocalStorage('name', 'Bob');
return (
<div>
<input value={name} onChange={(e) => setName(e.target.value)} />
<p>Hello, {name}!</p>
</div>
);
}
32. useScrollPosition
Tracks scroll position.
import { useEffect, useState } from 'react';
function useDebounce(value, delay) {
const [debouncedValue, setDebouncedValue] = useState(value);
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value);
}, delay);
return () => {
clearTimeout(handler);
};
}, [value, delay]);
return debouncedValue;
}
function App() {
const [text, setText] = useState('');
const debouncedText = useDebounce(text, 500);
return (
<div>
<input value={text} onChange={(e) => setText(e.target.value)} />
<p>Debounced Value: {debouncedText}</p>
</div>
);
}
33. useUnmount
Runs a function when a component unmounts.
import { useEffect, useRef } from 'react';
function usePrevious(value) {
const ref = useRef();
useEffect(() => {
ref.current = value;
}, [value]);
return ref.current;
}
function App() {
const [count, setCount] = useState(0);
const previousCount = usePrevious(count);
return (
<div>
<button onClick={() => setCount(count + 1)}>Count: {count}</button>
<p>Previous Count: {previousCount}</p>
</div>
);
}
34. useClickOutside
Detects clicks outside an element.
import { useEffect, useState } from 'react';
function useWindowSize() {
const [size, setSize] = useState({ width: window.innerWidth, height: window.innerHeight });
useEffect(() => {
const handleResize = () => {
setSize({ width: window.innerWidth, height: window.innerHeight });
};
window.addEventListener('resize', handleResize);
return () => window.removeEventListener('resize', handleResize);
}, []);
return size;
}
function App() {
const { width, height } = useWindowSize();
return (
<div>
<p>Width: {width}px</p>
<p>Height: {height}px</p>
</div>
);
}
35. useDebouncedCallback
Debounces a callback function.
import { useCallback, useState } from 'react';
function useHover() {
const [hovered, setHovered] = useState(false);
const onMouseOver = useCallback(() => setHovered(true), []);
const onMouseOut = useCallback(() => setHovered(false), []);
return { hovered, onMouseOver, onMouseOut };
}
function HoverComponent() {
const { hovered, onMouseOver, onMouseOut } = useHover();
return (
<div onMouseOver={onMouseOver} onMouseOut={onMouseOut}>
{hovered ? 'Hovering' : 'Not Hovering'}
</div>
);
}
36. useThrottle
Throttles a value over time.
import { useEffect, useState } from 'react';
function useOnlineStatus() {
const [isOnline, setIsOnline] = useState(navigator.onLine);
useEffect(() => {
const handleOnline = () => setIsOnline(true);
const handleOffline = () => setIsOnline(false);
window.addEventListener('online', handleOnline);
window.addEventListener('offline', handleOffline);
return () => {
window.removeEventListener('online', handleOnline);
window.removeEventListener('offline', handleOffline);
};
}, []);
return isOnline;
}
function App() {
const isOnline = useOnlineStatus();
return <div>{isOnline ? 'Online' : 'Offline'}</div>;
}
37. useUpdateEffect
Runs an effect only on updates, not on mount.
import { useEffect, useRef } from 'react';
function useEventListener(eventName, handler, element = window) {
const savedHandler = useRef();
useEffect(() => {
savedHandler.current = handler;
}, [handler]);
useEffect(() => {
const eventListener = (event) => savedHandler.current(event);
element.addEventListener(eventName, eventListener);
return () => {
element.removeEventListener(eventName, eventListener);
};
}, [eventName, element]);
}
function App() {
useEventListener('click', () => alert('Window clicked!'));
return <div>Click anywhere!</div>;
}
38.useLocalStorage
Manages state in local storage
import { useEffect, useRef } from 'react';
function useInterval(callback, delay) {
const savedCallback = useRef();
useEffect(() => {
savedCallback.current = callback;
}, [callback]);
useEffect(() => {
function tick() {
savedCallback.current();
}
if (delay !== null) {
const id = setInterval(tick, delay);
return () => clearInterval(id);
}
}, [delay]);
}
function Timer() {
const [count, setCount] = useState(0);
useInterval(() => setCount(count + 1), 1000);
return <div>Count: {count}</div>;
}
React.js is easy to learn and master, with numerous free courses and resources, plus a massive and active developer community
Make sure to use these React hooks in your next project and follow me for more content like this
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Understanding Event Bubbling and Capturing in JavaScript DOM events
Jul 08, 2025 am 02:36 AM
Event bubbles propagate from the target element outward to the ancestor node, while event capture propagates from the outer layer inward to the target element. 1. Event bubbles: After clicking the child element, the event triggers the listener of the parent element upwards in turn. For example, after clicking the button, it outputs Childclicked first, and then Parentclicked. 2. Event capture: Set the third parameter to true, so that the listener is executed in the capture stage, such as triggering the capture listener of the parent element before clicking the button. 3. Practical uses include unified management of child element events, interception preprocessing and performance optimization. 4. The DOM event stream is divided into three stages: capture, target and bubble, and the default listener is executed in the bubble stage.
A JS roundup of higher-order functions beyond map and filter
Jul 10, 2025 am 11:41 AM
In JavaScript arrays, in addition to map and filter, there are other powerful and infrequently used methods. 1. Reduce can not only sum, but also count, group, flatten arrays, and build new structures; 2. Find and findIndex are used to find individual elements or indexes; 3.some and everything are used to determine whether conditions exist or all meet; 4.sort can be sorted but will change the original array; 5. Pay attention to copying the array when using it to avoid side effects. These methods make the code more concise and efficient.
