React Hooks, the powerful feature introduced in React 16.8. React Hooks are functions that allow you to use state and other React features in functional components, making it easier to manage stateful logic and reuse code. In this article, we will dive into a comprehensive list of React Hooks and explore how they work, providing practical examples along the way.
Contents
useState
What is the “useState” Hook?
The “useState” hook is a built-in React hook that enables functional components to manage state without the need for class components. It provides a way to add stateful logic to functional components, allowing you to build dynamic and interactive user interfaces with ease. Prior to the introduction of hooks in React 16.8, developers had to use class components to manage state, which could lead to complex and cumbersome code. With the “useState” hook, you can now achieve the same functionality with cleaner and more concise code.
How Does “useState” Work?
Using the “useState” hook is straightforward. To use it in your functional component, you need to import it from the “react” package. The hook takes an initial state as an argument and returns an array with two elements: the current state value and a function to update the state. Here’s a basic example of how to use “useState”:
import React, { useState } from 'react';
function Counter() {
// Declare a state variable named "count" with an initial value of 0
const [count, setCount] = useState(0);
// Render the component with the current "count" state
return (
); }
Updating State with “useState”
To update the state managed by “useState,” you simply call the setter function returned by the hook. In the example above, we use “setCount” to increment the “count” state whenever the button is clicked. React will automatically re-render the component with the updated state value.
Benefits of “useState”
The “useState” hook offers several benefits for React developers:
- Simplified State Management: With “useState,” you can manage state directly in functional components, reducing the need for class components and making your code more concise.
- Improved Performance: React hooks are optimized for performance, allowing you to build efficient and performant applications.
- Code Reusability: Functional components are highly reusable, and by using hooks like “useState,” you can create modular and easily maintainable code.
- Readability: Hooks lead to more readable code, making it easier for you and your team to understand and maintain the application.
useEffect
What is the “useEffect” Hook?
The “useEffect” hook is a built-in React hook that enables functional components to perform side effects. Side effects refer to any operation that affects the external world, such as fetching data from an API, subscribing to events, or manipulating the DOM. Prior to the introduction of hooks in React 16.8, managing side effects required the use of lifecycle methods in class components. With the “useEffect” hook, you can now handle side effects in functional components in a more declarative and concise manner.
How Does “useEffect” Work?
Using the “useEffect” hook is simple yet powerful. To use it in your functional component, you need to import it from the “react” package. The hook takes two arguments: a function that represents the side effect you want to perform and an optional array of dependencies. Here’s a basic example of how to use “useEffect”:
import React, { useEffect, useState } from 'react';
function DataFetcher() {
const [data, setData] = useState([]);
useEffect(() => {
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => setData(data));
}, []);
return (
); }
Dependency Array in “useEffect”
The second argument of “useEffect” is an array of dependencies. By providing dependencies, you can control when the side effect is executed. If the dependency array is empty, the side effect will run only once when the component mounts. If you provide specific dependencies, the side effect will run whenever any of these dependencies change. This ensures that the side effect is executed at the right time and avoids unnecessary re-renders.
Common Use Cases for “useEffect”
The “useEffect” hook is widely used for various scenarios, including:
- Fetching data from APIs
- Subscribing to event listeners
- Updating the DOM after render
- Cleaning up resources or subscriptions
- Managing animations and transitions
useContext
What is the “useContext” Hook?
The “useContext” hook is one of the built-in hooks in React, introduced in version 16.8. It allows you to consume data from a React context without the need for intermediate components to pass down props. Contexts provide a way to share data among components without explicitly passing it through props, making your codebase more maintainable and avoiding prop drilling.
How Does “useContext” Work?
Using the “useContext” hook involves two primary steps:
- Create a context: First, you need to create a context using the “createContext” function from the “react” package. This context will hold the shared data that you want to make available to other components.
- Consume the context: Next, you can consume the context and access its data within your components using the “useContext” hook. The hook takes the context object as an argument and returns the current context value.
// Step 1: Create a context
import { createContext, useContext } from 'react';
const ThemeContext = createContext();
// Step 2: Consume the context
function ThemedButton() {
const theme = useContext(ThemeContext);
return (
);
}
Benefits of “useContext”
The “useContext” hook offers several advantages when managing global state in your React applications:
- Eliminates Prop Drilling: With “useContext,” you can avoid the complexity of passing props through multiple components, enhancing code readability and maintainability.
- Centralized State Management: Contexts provide a centralized way to manage and share state across different parts of your application.
- Reduced Boilerplate: By using “useContext,” you can eliminate the need for intermediate components, reducing boilerplate code in your app.
- Efficient Updates: React optimizes updates with contexts, ensuring that only the components that depend on the context value are re-rendered when it changes.
- Improved Developer Experience: “useContext” simplifies the process of accessing global state, leading to a more enjoyable development experience.
useReducer
What is the “useReducer” Hook?
The “useReducer” hook is a powerful alternative to “useState” when it comes to managing state in React. It allows you to handle complex state logic using a reducer function, similar to how you manage state in traditional JavaScript applications using “switch” statements. While “useState” is sufficient for managing simple state changes, “useReducer” is more suitable for scenarios involving complex state transitions.
How Does “useReducer” Work?
The “useReducer” hook takes two arguments: a reducer function and an initial state. The reducer function is responsible for specifying how state updates should be processed based on the dispatched action. It takes the current state and the action as arguments and returns the new state. Here’s a basic example of how to use “useReducer”:
import React, { useReducer } from 'react';
const initialState = { count: 0 };
function countReducer(state, action) {
switch (action.type) {
case 'increment':
return { count: state.count + 1 };
case 'decrement':
return { count: state.count - 1 };
default:
return state;
}
}
function Counter() {
const [state, dispatch] = useReducer(countReducer, initialState);
return (
); }
Benefits of “useReducer”
The “useReducer” hook offers several benefits in managing state:
- Complex State Management: “useReducer” simplifies handling complex state transitions, making it easier to manage state logic.
- Centralized Updates: The reducer function centralizes state updates, which can help prevent inconsistencies and bugs in your application.
- Reusable Logic: You can reuse the same reducer function across multiple components, promoting code reusability and maintainability.
- Enhanced Predictability: Reducers follow a predictable pattern, making it easier to reason about state changes in your app.
- Testability: The reducer function can be easily tested in isolation to ensure the correctness of state transitions.
useCallback
What is the “useCallback” Hook?
The “useCallback” hook is one of the built-in hooks in React, introduced in version 16.8. It is used to optimize the rendering behavior of functional components by memoizing functions. When a component renders, its functions are recreated, which can lead to unnecessary re-renders in child components. “useCallback” memoizes the function, ensuring that it remains the same between renders unless its dependencies change.
How Does “useCallback” Work?
The “useCallback” hook takes two arguments: the callback function and an array of dependencies. The hook returns a memoized version of the function. The function will only be re-created if one of the dependencies in the array changes. Here’s a basic example of how to use “useCallback”:
import React, { useState, useCallback } from 'react';
function MemoizedButton({ onClick }) {
return ;
}
function App() {
const [count, setCount] = useState(0);
// Using useCallback to memoize the event handler
const handleClick = useCallback(() => {
setCount(count + 1);
}, [count]);
return (
); }
Benefits of “useCallback”
The “useCallback” hook offers several advantages when it comes to optimizing performance:
- Reduced Re-renders: By memoizing functions, “useCallback” reduces unnecessary re-renders in child components, improving overall performance.
- Stable References: “useCallback” ensures that the function reference remains stable between renders, which is essential for correct prop comparison in React.
- Improved Performance: The optimization achieved with “useCallback” is especially beneficial when dealing with large-scale applications and complex components.
- Enhanced Developer Experience: Utilizing “useCallback” leads to a better development experience, as it helps in identifying and addressing performance bottlenecks.
useMemo
What is the “useMemo” Hook?
The “useMemo” hook is one of the built-in hooks in React, introduced in version 16.8. It is used to memoize the result of a function so that it can be reused in subsequent renders. This optimization prevents the recalculation of expensive computations unless the dependencies provided to “useMemo” change.
How Does “useMemo” Work?
The “useMemo” hook takes two arguments: the computation function and an array of dependencies. The hook returns the memoized result of the computation function. The function will only be recomputed if one of the dependencies in the array changes. Here’s a basic example of how to use “useMemo”:
import React, { useState, useMemo } from 'react';
function computeExpensiveValue(a, b) {
console.log('Computing...');
return a + b;
}
function App() {
const [valueA, setValueA] = useState(5);
const [valueB, setValueB] = useState(10);
// Using useMemo to memoize the result of computeExpensiveValue
const result = useMemo(() => computeExpensiveValue(valueA, valueB), [valueA, valueB]);
return (
); }
Benefits of “useMemo”
The “useMemo” hook offers several advantages when it comes to performance optimization:
- Performance Improvement: By memoizing expensive computations, “useMemo” reduces unnecessary recalculations and improves rendering performance.
- Efficient Rendering: Components using “useMemo” are more efficient, as they only update when necessary, resulting in a smoother user experience.
- Enhanced Developer Control: Developers have more control over which computations are memoized and can fine-tune the optimization to suit specific use cases.
- Optimized Re-renders: Memoization helps prevent redundant re-renders, especially in complex applications with numerous computations.
useRef
What is the “useRef” Hook?
The “useRef” hook is one of the built-in hooks in React, introduced in version 16.8. It is used to create a mutable reference that persists across renders. Unlike state, changing the “useRef” value does not trigger a re-render of the component. The “useRef” hook is commonly used to access and modify DOM elements, manage timers and intervals, and store any mutable value that needs to be retained between renders.
How Does “useRef” Work?
The “useRef” hook returns a mutable ref object that has a “current” property. The “current” property can be assigned any value, and it will persist across renders. When the “useRef” hook is used in a functional component, it will always return the same ref object between renders, ensuring that the value it holds remains intact. Here’s a basic example of how to use “useRef”:
import React, { useRef, useEffect } from 'react';
function InputComponent() {
const inputRef = useRef(null);
useEffect(() => {
inputRef.current.focus();
}, []);
return ;
}
Benefits of “useRef”
The “useRef” hook offers several advantages when it comes to working with React components:
- DOM Manipulation: “useRef” allows direct access to DOM elements, making it easy to manipulate focus, scroll position, and other DOM-related operations.
- Persistent Values: Unlike state, the values stored in “useRef” persist across renders and do not trigger re-renders when modified.
- Improved Performance: Since “useRef” does not cause re-renders, it is an efficient way to store and update values without affecting the component’s rendering cycle.
- Managing Uncontrolled Components: “useRef” is often used to manage uncontrolled components, such as managing form inputs and accessing their values directly.
useImperativeHandle
What is the “useImperativeHandle” Hook?
The “useImperativeHandle” hook is one of the built-in hooks in React, introduced in version 16.8. It allows a child component to customize the instance value that is exposed to parent components when using “ref” to access the child component. This customization enables the parent component to interact with specific functions or values of the child component directly.
How Does “useImperativeHandle” Work?
The “useImperativeHandle” hook takes two arguments: the “ref” object that is being forwarded, and a callback function that returns the value to be exposed to the parent component. The callback function is executed on every render, and it allows you to determine what values or functions to expose. Here’s a basic example of how to use “useImperativeHandle”:
import React, { useRef, useImperativeHandle, forwardRef } from 'react';
const ChildComponent = forwardRef((props, ref) => {
const inputRef = useRef(null);
// Expose a function to focus the input element
useImperativeHandle(ref, () => ({
focusInput: () => {
inputRef.current.focus();
}
}));
return ;
});
// Parent component
function ParentComponent() {
const childRef = useRef(null);
const handleFocusInput = () => {
childRef.current.focusInput();
};
return (
); }
Benefits of “useImperativeHandle”
The “useImperativeHandle” hook offers several advantages when it comes to communication between parent and child components:
- Explicit API: “useImperativeHandle” provides an explicit API for parent components to interact with specific functions or values of the child component, enhancing code clarity and maintainability.
- Encapsulation: The hook promotes encapsulation by allowing the child component to expose only the necessary functions or values to the parent, preventing unwanted access to internal details.
- Functional Programming: With “useImperativeHandle,” you can follow functional programming principles and pass behavior as props to child components, enabling more flexible and reusable code.
- Customization: Parent components can customize the instance value exposed by the child component, tailoring it to suit their specific requirements.
useLayoutEffect
What is the “useLayoutEffect” Hook?
The “useLayoutEffect” hook is similar to the useEffect hook in that it allows you to perform side effects in function components. However, it differs in the timing of its execution. While useEffect runs asynchronously after the browser has rendered the component and performed layout changes, useLayoutEffect runs synchronously before the browser performs any painting or layout updates. This makes it suitable for situations where you need to make changes before the browser updates the screen.
When to Use “useLayoutEffect”?
Since “useLayoutEffect” runs synchronously, you should use it with caution and only when it’s necessary. Here are some scenarios where “useLayoutEffect” can be beneficial:
- DOM Measurements: If you need to measure DOM elements’ dimensions or positions and make adjustments based on these measurements, “useLayoutEffect” ensures that you get accurate measurements before the browser updates the layout.
- Animating Layout Changes: When animating layout changes, using “useLayoutEffect” can help in avoiding flickering or visual glitches by applying the changes before the browser renders the component.
- Updating Styles: If you need to update styles that affect the component’s layout, “useLayoutEffect” ensures that the changes are applied before the browser performs the layout updates.
Example of “useLayoutEffect”
Let’s look at an example of how to use “useLayoutEffect” to measure the width of an element and update its style accordingly:
import React, { useLayoutEffect, useRef, useState } from 'react';
function ResizeComponent() {
const [width, setWidth] = useState(0);
const ref = useRef(null);
useLayoutEffect(() => {
const handleResize = () => {
if (ref.current) {
setWidth(ref.current.clientWidth);
}
};
return () => {
window.removeEventListener('resize', handleResize);
};
}, []);
return (
Width: {width}px
); }
handleResize(); // Get initial width
window.addEventListener('resize', handleResize);
useDebugValue
What is the “useDebugValue” Hook?
The “useDebugValue” hook is a special hook in React that allows you to display custom labels for hooks in React DevTools. It is not used for any functional purposes in the component itself but rather for enhancing the debugging experience. With “useDebugValue”, you can provide a custom label or description to better identify hooks when inspecting React components in the DevTools.
When and How to Use “useDebugValue”?
You can use “useDebugValue” when you want to provide more descriptive information about a custom hook you have created. This can be helpful for understanding the hook’s behavior when inspecting it in the React DevTools.
Here’s how you can use “useDebugValue”:
import { useDebugValue, useState } from 'react';
function useCustomHook(initialValue) {
const [state, setState] = useState(initialValue);
// Custom logic for your hook
// Providing a custom label for the hook in React DevTools
useDebugValue('Custom Hook: ' + initialValue);
return state;
}
Example of “useDebugValue”
Let’s look at an example of how “useDebugValue” can improve the debugging experience for a custom hook:
import React from 'react';
function useCustomHook(initialValue) {
const [state, setState] = React.useState(initialValue);
// Custom logic for your hook
// Providing a custom label for the hook in React DevTools
React.useDebugValue('Custom Hook: ' + initialValue);
return state;
}
function Component() {
const value = useCustomHook(0);
return (
); }
useDeferredValue
What is the “useDeferredValue” Hook?
The “useDeferredValue” hook is a new addition introduced in React 18 to optimize concurrent rendering in concurrent mode. It is designed to help you improve the user experience when working with data that changes rapidly. The hook allows you to get a deferred version of the provided value, meaning that it gives you the previous value during a render, while the current value is calculated asynchronously.
How Does “useDeferredValue” Work?
The “useDeferredValue” hook is particularly useful when dealing with fast-changing data, such as animations or frequently updated user inputs. By using this hook, you can display the previously committed value to the user during a render, providing a smoother and less jarring user experience.
Example of “useDeferredValue”
Let’s look at an example of how “useDeferredValue” can be used:
import React, { useDeferredValue } from 'react';
function Component() {
const [count, setCount] = React.useState(0);
// Get the deferred value of 'count'
const deferredCount = useDeferredValue(count);
// Fast-changing data
React.useEffect(() => {
const interval = setInterval(() => {
setCount((prevCount) => prevCount + 1);
}, 100);
return () => clearInterval(interval);
}, []);
return (
); }
useTransition
What is the “useTransition” Hook?
The “useTransition” hook is a new addition introduced in React 18 to handle asynchronous rendering in concurrent mode. It allows you to wrap a section of your UI that might be slow to render or update, giving you control over how React handles these updates and transitions. This enables you to create smoother user experiences and improve perceived performance, especially in situations where there might be a noticeable delay between user interactions and UI updates.
How Does “useTransition” Work?
The “useTransition” hook works by allowing you to wrap a part of your UI with a transition boundary. Within this boundary, React will transition from the old state to the new state in a more controlled manner. During the transition, you can show a fallback UI to the user to avoid janky updates, giving the impression of a more responsive application.
Example of “useTransition”
Here’s an example of how you can use the “useTransition” hook:
import React, { useState, useTransition } from 'react';
function Component() {
const [show, setShow] = useState(false);
const [startTransition, isPending] = useTransition({
timeoutMs: 3000,
});
const handleClick = () => {
startTransition(() => {
setShow(!show);
});
};
return (
); }
useId
What is the “useId” Hook?
The “useId” hook is a custom hook commonly used in React applications to generate unique identifiers. It comes in handy when you need to assign a unique ID to a dynamically created element, such as a list item or a form input. By using “useId,” you can ensure that each element receives a unique ID, avoiding conflicts and ensuring smooth interactions.
How Does “useId” Work?
The “useId” hook works by generating a unique ID every time it is called. It uses a counter to keep track of the number of IDs generated and appends it to a base string to create the unique ID. The hook takes an optional prefix parameter, allowing you to customize the ID to suit your needs.
Example of “useId”
Here’s an example of how you can use the “useId” hook:
import React from 'react';
import { useId } from 'react-id-generator';
function Component() {
const [inputId] = useId();
return (
); }
useSyncExternalStore
What is the “useSyncExternalStore” Hook?
The “useSyncExternalStore” hook is a custom hook that facilitates the synchronization of state between your React components and an external state management system, such as Redux or MobX. It acts as a bridge between your React application and the external store, ensuring that the data remains consistent and up-to-date across all components.
How Does “useSyncExternalStore” Work?
The “useSyncExternalStore” hook works by integrating with an external state management system and exposing the state and state-update functions to your React components. It handles the synchronization of data between your components and the external store, allowing you to maintain a single source of truth for your application’s state.
Example of “useSyncExternalStore”
Here’s a simplified example of how you can use the “useSyncExternalStore” hook with Redux:
import React from 'react';
import { useSyncExternalStore } from 'your-favorite-state-management-library';
function Component() {
const { data, setData } = useSyncExternalStore('todos', initialState);
const handleAddTodo = (todo) => {
setData([...data, todo]);
};
return (
-
- {data.map((todo) => (
- {todo.text}
))}
); }
useInsertionEffect
What is the “useInsertionEffect” Hook?
The “useInsertionEffect” hook is a custom hook in React that enables you to perform side effects only when a component is inserted into the DOM. Unlike “useEffect,” which triggers side effects on every render, “useInsertionEffect” runs the effect only once during the initial render of the component. This can be particularly useful when you want to execute certain actions or set up event listeners when the component is first added to the DOM.
How Does “useInsertionEffect” Work?
The “useInsertionEffect” hook is similar to the familiar “useEffect” hook in its syntax and usage. The key difference is that “useInsertionEffect” accepts a dependency array as the second argument, but it ignores the dependencies completely and runs the effect only once during component insertion. This ensures that the effect doesn’t execute unnecessarily during subsequent renders, which can lead to more efficient and optimized code.
Example of “useInsertionEffect”
Here’s a simple example of how you can use the “useInsertionEffect” hook:
import React from 'react';
import { useInsertionEffect } from 'react-hooks-library';
function WelcomeMessage() {
useInsertionEffect(() => {
alert('Welcome! This message is shown only once during component insertion.');
}, []);
return (
); }