React has been a game-changer in the world of web development. It's time to explore the exciting world of hooks. React introduces a plethora of hooks to simplify your component logic, making your code more efficient and maintainable. In this article, we'll delve into 15 new hooks that come with React 18, explaining their usage and providing real-world examples.
No. | React Hook |
---|---|
1. | useState |
2. | useReducer |
3. | useContext |
4. | useEffect |
5. | useLayoutEffect |
6. | useDebugValue |
7. | useRef |
8. | useImperativeHandle |
9. | useCallback |
10. | useMemo |
11. | useLocation |
12. | useHistory |
13. | useParams |
14. | useTransition |
15. | useDeferredValue |
16. | custom hooks |
-
useState
is one of the most commonly used React hooks, introduced in React 16.8. It allows functional components to manage and update their internal state, making them dynamic and responsive. WithuseState
, you can declare state variables and easily update them, triggering re-renders when the state changes.Example of
useState
in ReactHere's a simple example of how to use
useState
in a React functional component:import React, { useState } from 'react'; function Counter() { // Declare a state variable named "count" with an initial value of 0 const [count, setCount] = useState(0); // Event handler to increment the count const incrementCount = () => { setCount(count 1); }; // Event handler to reset the count const resetCount = () => { setCount(0); }; return ( <div> <p>Count: {count}</p> <button onClick={incrementCount}>Increment</button> <button onClick={resetCount}>Reset</button> </div> ); } export default Counter;
In this example, we create a
Counter
component using theuseState
hook. Here's a breakdown of what's happening:-
We import React and the
useState
hook from the 'react' library. -
Inside the
Counter
component, we declare a state variable namedcount
using theuseState
hook. The initial value ofcount
is set to 0. TheuseState
function returns an array with two elements: the current state value (count
) and a function to update that state (setCount
). -
We define two event handlers,
incrementCount
andresetCount
, which use thesetCount
function to update thecount
state. WhensetCount
is called, it triggers a re-render of the component with the new state value. -
In the component's JSX, we display the current count value, and there are two buttons. Clicking the "Increment" button calls the
incrementCount
function, and clicking the "Reset" button calls theresetCount
function, updating the count accordingly.
The
useState
hook simplifies state management in functional components, making it easy to handle and update component-specific data. It allows you to create interactive and dynamic user interfaces without the need for class components or complex state management code. -
-
useReducer
is a React hook that is used to manage state in a more structured and predictable way. It is especially useful when you have state that depends on the previous state and when you need to handle complex state transitions and logic.Example of
useReducer
in ReactHere's an example of how to use
useReducer
in a React functional component:import React, { useReducer } from 'react'; // Define a reducer function function counterReducer(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(counterReducer, { count: 0 }); return ( <div> <p>Count: {state.count}</p> <button onClick={() => dispatch({ type: 'increment' })}>Increment</button> <button onClick={() => dispatch({ type: 'decrement' })}>Decrement</button> </div> ); } export default Counter;
In this example, we create a counter component using the
useReducer
hook. ThecounterReducer
function defines how the state should be updated based on different actions, and thedispatch
function is used to dispatch these actions.State Hooks, whether
useState
oruseReducer
, have transformed the way we handle state in React. They have brought simplicity, clarity, and reusability to state management, making React applications more efficient and maintainable.In this article, we'll explore these hooks in greater depth, provide examples of their usage, and discuss best practices to help you become proficient in managing state in your React applications.
-
useContext
is a React hook that allows functional components to access context values. Context in React is a way to share data that can be considered "global" to a component tree, without manually passing it through props at each level.Example of
useContext
in ReactIn this example, we'll create a simple theme-switching application that uses
useContext
to share the current theme throughout the component tree.Step 1: Create a Theme Context
First, define a theme context with an initial theme value:
// ThemeContext.js import React, { createContext, useContext, useState } from 'react'; const ThemeContext = createContext(); export function ThemeProvider({ children }) { const [theme, setTheme] = useState('light'); const toggleTheme = () => { setTheme(theme === 'light' ? 'dark' : 'light'); }; return ( <ThemeContext.Provider value={{ theme, toggleTheme }}> {children} </ThemeContext.Provider> ); } export function useTheme() { return useContext(ThemeContext); }
In this code:
- We create a
ThemeContext
using thecreateContext
function. - We define a
ThemeProvider
component that manages the theme state and provides the theme value and a function to toggle the theme using theuseState
hook. - The
useTheme
custom hook allows us to easily access the theme and toggle function.
Step 2: Using
useContext
to Consume the ContextNow, let's use the theme context in our components:
// App.js import React from 'react'; import { ThemeProvider, useTheme } from './ThemeContext'; import ThemeSwitcher from './ThemeSwitcher'; function App() { return ( <ThemeProvider> <div className="App"> <Header /> <Content /> </div> </ThemeProvider> ); } function Header() { const { theme } = useTheme(); return ( <header className={`header ${theme}`}> <h1>My Theme App</h1> <ThemeSwitcher /> </header> ); } function Content() { const { theme } = useTheme(); return ( <div className={`content ${theme}`}> <p>This is the content of my app.</p> </div> ); } export default App;
In this code:
- We wrap our
App
component with theThemeProvider
, which provides the theme context. - Inside the
Header
andContent
components, we use theuseTheme
custom hook to access the theme value. - The theme value is applied to the
className
of the elements, allowing us to switch between "light" and "dark" themes.
Step 3: Create the ThemeSwitcher Component
Let's create a component to switch between themes:
// ThemeSwitcher.js import React from 'react'; import { useTheme } from './ThemeContext'; function ThemeSwitcher() { const { theme, toggleTheme } = useTheme(); return ( <button onClick={toggleTheme}> Switch to {theme === 'light' ? 'dark' : 'light'} mode </button> ); } export default ThemeSwitcher;
In this component, we use the
useTheme
custom hook to access thetheme
andtoggleTheme
function to switch between light and dark themes.By using the
useContext
hook along with a custom hook, you can efficiently access and manage shared state or data within your React application without the need for prop drilling, making your code more maintainable and clean. - We create a
-
useEffect
is a React Hook that allows you to perform side effects in functional components. It's equivalent to the lifecycle methodscomponentDidMount
,componentDidUpdate
, andcomponentWillUnmount
in class components. WithuseEffect
, you can execute code after the component has rendered and react to changes in props and state.Example of
useEffect
in ReactIn this example, we'll create a simple React component that fetches and displays data from an API when the component is mounted.
import React, { useState, useEffect } from 'react'; function DataFetchingComponent() { const [data, setData] = useState([]); const [loading, setLoading] = useState(true); useEffect(() => { // This code block runs after the component has rendered fetch('https://api.example.com/data') // Replace with your API endpoint .then((response) => response.json()) .then((result) => { setData(result); setLoading(false); }) .catch((error) => { console.error('Error fetching data: ', error); setLoading(false); }); }, []); // The empty dependency array means this effect runs only on component mount return ( <div> {loading ? ( <p>Loading...</p> ) : ( <ul> {data.map((item) => ( <li key={item.id}>{item.name}</li> ))} </ul> )} </div> ); } export default DataFetchingComponent;
In this code:
- We import React,
useState
, anduseEffect
from 'react'. - We create a functional component called
DataFetchingComponent
. - Inside the component, we declare state variables
data
andloading
using theuseState
hook. - We use the
useEffect
hook to fetch data from an API when the component is mounted. The empty dependency array[]
indicates that this effect should only run once after the initial render.
Here's a step-by-step explanation of what's happening:
-
When the component is mounted, the
useEffect
code block fetches data from the API using thefetch
function. -
Once the data is fetched, it's processed, and the state is updated using the
setData
andsetLoading
functions, which triggers a re-render. -
The component renders either a "Loading..." message or a list of data items based on the
loading
state.
Using
useEffect
, you can easily manage asynchronous operations, data fetching, and other side effects within your functional components. It helps keep your components clean, efficient, and responsive to changes. - We import React,
-
useLayoutEffect
is a React Hook that is similar touseEffect
. The key difference is the timing of when the effect runs.useLayoutEffect
runs synchronously after the DOM is mutated but before the browser repaints. This makes it ideal for tasks that require immediate DOM changes.Example of
useLayoutEffect
in ReactIn this example, we'll create a React component that uses
useLayoutEffect
to change the background color of a button element immediately after it's rendered. This demonstrates howuseLayoutEffect
can be useful for tasks that require changes to the DOM before it's painted.import React, { useState, useLayoutEffect } from 'react'; function ButtonComponent() { const [backgroundColor, setBackgroundColor] = useState('white'); useLayoutEffect(() => { setBackgroundColor('blue'); // Change the background color immediately after rendering }, []); // The empty dependency array means this effect runs only once after the initial render return ( <button style={{ backgroundColor }}>Click me</button> ); } export default ButtonComponent;
In this code:
- We import React,
useState
, anduseLayoutEffect
from 'react'. - We create a functional component called
ButtonComponent
. - Inside the component, we declare a state variable
backgroundColor
using theuseState
hook.
The key part is the
useLayoutEffect
:-
The
useLayoutEffect
code block changes thebackgroundColor
state variable to 'blue' immediately after rendering, thanks to the synchronous nature ofuseLayoutEffect
. -
The component renders a button element with a dynamic background color based on the
backgroundColor
state.
When the component is rendered, the button's background color changes to 'blue' without waiting for the next browser paint. This demonstrates how
useLayoutEffect
can be useful for tasks that require immediate DOM changes, ensuring a smoother user experience.Keep in mind that, in most cases, you'll use the standard
useEffect
hook for handling side effects, as it doesn't block the painting phase.useLayoutEffect
is generally used for very specific scenarios where synchronous DOM mutations are required. - We import React,
-
useDebugValue
is a hook that enables you to provide additional information about your custom hooks for React DevTools. It's particularly useful when creating custom hooks that encapsulate complex logic or state management, making it easier to understand and debug the behavior of these hooks.Example of
useDebugValue
in a Custom HookIn this example, we'll create a simple custom hook called
useCounter
that counts and displays a value. We'll useuseDebugValue
to provide a label for React DevTools.import { useState, useEffect, useDebugValue } from 'react'; function useCounter(initialValue) { const [count, setCount] = useState(initialValue); useEffect(() => { document.title = `Count: ${count}`; }, [count]); useDebugValue(count, (count) => `Custom Counter: ${count}`); // Debug label return { count, increment: () => setCount(count 1) }; } export default useCounter;
In this code:
-
We import React's
useState
,useEffect
, anduseDebugValue
hooks. -
We create a custom hook named
useCounter
that takes an initial value and returns an object with the currentcount
value and anincrement
function to increase the count. -
Inside the
useEffect
, we update the document title with the current count whenever thecount
changes. -
The key part is the
useDebugValue
hook. We use it to provide a label and value for React DevTools. This allows you to see a more informative label in DevTools when inspecting this custom hook. The custom label is created based on the count value.
Using the
useCounter
custom hookNow, you can use the
useCounter
custom hook in your components:import React from 'react'; import useCounter from './useCounter'; function CounterComponent() { const counter = useCounter(0); return ( <div> <p>Count: {counter.count}</p> <button onClick={counter.increment}>Increment</button> </div> ); } export default CounterComponent;
In this component, we use the
useCounter
custom hook to manage the count state and increment function. The custom label provided byuseDebugValue
will be visible in React DevTools when inspecting theuseCounter
hook.This example demonstrates how
useDebugValue
can be used to improve the debugging experience when creating custom hooks by providing informative labels for custom hooks in React DevTools. It's especially helpful for hooks that encapsulate complex logic or state management. -
-
useRef
is a Hook that provides a way to reference and interact with DOM elements and other values in a functional component. It is commonly used when you need to access the underlying DOM, manage values that don't trigger re-renders, or perform actions that require direct manipulation.Example of
useRef
in ReactIn this example, we'll use
useRef
to focus an input element when the component mounts:import React, { useRef, useEffect } from 'react'; function FocusInput() { // Create a ref to store a reference to the input element const inputRef = useRef(null); // Use useEffect to focus the input element when the component mounts useEffect(() => { inputRef.current.focus(); }, []); return ( <div> <p>Click the button to focus the input field:</p> <input ref={inputRef} /> </div> ); } export default FocusInput;
In this code:
-
We import React,
useRef
, anduseEffect
from 'react'. -
Inside the
FocusInput
component, we create a ref usinguseRef
. The initial value of the ref is set tonull
. -
We use the
useEffect
hook to focus the input element when the component mounts. We do this by callinginputRef.current.focus()
. -
In the component's JSX, we render a paragraph and an input field. We attach the
inputRef
to theref
attribute of the input element. -
When the component mounts, the
useEffect
is triggered, and it callsinputRef.current.focus()
, which focuses the input field.
This is just a basic example of how to use
useRef
to access and interact with DOM elements. You can also useuseRef
to store and manipulate values, including custom data, without causing re-renders in your component.useRef
is a versatile tool for handling various scenarios in React. -
-
useImperativeHandle
is a Hook that gives you control over what is exposed when a parent component uses aref
to access a child component. It allows you to customize the instance value that the parent component sees, making it possible to expose only the methods or properties that are relevant.Example of
useImperativeHandle
in ReactChild Component (Child.js):
import React, { useImperativeHandle, forwardRef } from 'react'; const Child = forwardRef((props, ref) => { // Create a local variable let count = 0; // Define a function that increments the count const incrementCount = () => { count = 1; }; // Expose the incrementCount function to the parent component useImperativeHandle(ref, () => ({ incrementCount, })); return ( <div> <p>Child Component</p> </div> ); }); export default Child;
In this code:
-
We import React,
useImperativeHandle
, andforwardRef
from 'react'. -
We create a functional child component called
Child
. -
Inside the
Child
component, we define a local variablecount
and a functionincrementCount
that increments thecount
. -
We use
useImperativeHandle
to expose theincrementCount
function to the parent component via theref
. This means the parent can access and call theincrementCount
function on the child component.
Parent Component (Parent.js):
import React, { useRef } from 'react'; import Child from './Child'; function Parent() { const childRef = useRef(); const handleIncrement = () => { childRef.current.incrementCount(); }; return ( <div> <p>Parent Component</p> <button onClick={handleIncrement}>Increment Child Count</button> <Child ref={childRef} /> </div> ); } export default Parent;
In this code:
-
We create a parent component called
Parent
. -
Inside the
Parent
component, we useuseRef
to create achildRef
that we will use to access the child component. -
We define a function
handleIncrement
that calls theincrementCount
function on the child component when a button is clicked. -
The
Child
component is rendered with aref
attribute that points to thechildRef
. This allows the parent to access the child component and call theincrementCount
function.
When you click the "Increment Child Count" button in the parent component, it calls the
incrementCount
function in the child component, incrementing thecount
variable in the child. This demonstrates howuseImperativeHandle
allows you to expose specific methods or properties of a child component to its parent, providing greater control and encapsulation of functionality. -
-
useCallback
is a React Hook that memoizes a function, creating a memoized version of the function that will only change if its dependencies change. This is beneficial when you want to optimize performance by avoiding re-creating functions on each render, especially when those functions are passed as props to child components.Example of
useCallback
in ReactIn this example, we'll create a simple counter application with two buttons, and we'll use
useCallback
to optimize the event handler functions.import React, { useState, useCallback } from 'react'; function Counter() { const [count, setCount] = useState(0); // Create memoized event handlers with useCallback const increment = useCallback(() => { setCount(count 1); }, [count]); const decrement = useCallback(() => { setCount(count - 1); }, [count]); return ( <div> <p>Count: {count}</p> <button onClick={increment}>Increment</button> <button onClick={decrement}>Decrement</button> </div> ); } export default Counter;
In this code:
-
We import React,
useState
, anduseCallback
from 'react'. -
Inside the
Counter
component, we declare a state variablecount
to hold the current count and an event handler functionsetCount
to update the count. -
We create two memoized event handlers,
increment
anddecrement
, usinguseCallback
. These event handlers update the count state by incrementing and decrementing it, respectively. -
We provide the
useCallback
hook with a dependency array. In this case, the dependency array contains thecount
variable, which indicates that the event handlers should only be recreated if thecount
value changes. -
In the component's JSX, we display the current count and two buttons with the memoized event handlers for increment and decrement.
By using
useCallback
, the event handlers are memoized and only recreated when thecount
variable changes. This optimization prevents unnecessary re-renders and can be especially useful in scenarios where you pass these functions as props to child components. It helps improve the performance of your React applications by ensuring that functions remain consistent and do not cause unnecessary re-renders. -
-
useMemo
is a React Hook that memoizes a value based on a function and a list of dependencies. It calculates the value once and then returns that memoized value on subsequent renders unless one of the dependencies has changed. This can be particularly useful when you need to optimize the calculation of derived data, heavy computations, or data transformations.Example of
useMemo
in ReactIn this example, we'll create a simple React component that calculates the factorial of a number using
useMemo
to optimize the computation:import React, { useState, useMemo } from 'react'; function FactorialCalculator({ number }) { const factorial = useMemo(() => calculateFactorial(number), [number]); function calculateFactorial(n) { if (n === 0 || n === 1) { return 1; } return n * calculateFactorial(n - 1); } return ( <div> <p>Factorial of {number} is {factorial}</p> </div> ); } export default FactorialCalculator;
In this code:
-
We import React,
useState
, anduseMemo
from 'react'. -
Inside the
FactorialCalculator
component, we receive anumber
prop, which is the input for which we want to calculate the factorial. -
We use the
useMemo
hook to memoize the result of thecalculateFactorial
function. The first argument touseMemo
is a function that performs the calculation, and the second argument is an array of dependencies. In this case, the dependency is thenumber
prop. The value is calculated only when thenumber
prop changes. -
The
calculateFactorial
function is a recursive function that calculates the factorial of a number. -
In the component's JSX, we display the calculated factorial.
By using
useMemo
, we ensure that thefactorial
value is calculated only when thenumber
prop changes. If thenumber
prop remains the same between renders, the memoizedfactorial
value is reused, preventing unnecessary re-computation and improving the performance of the component.useMemo
is especially valuable when you have expensive computations or data transformations in your components. It optimizes your application by ensuring that calculations are performed only when necessary and reusing previously calculated results when the dependencies don't change. -
-
The
useLocation
hook is commonly used in React applications that use thereact-router-dom
library for client-side routing. It provides access to the current location object, allowing you to examine and work with the various parts of the URL, such as the pathname and search parameters. This is useful for creating dynamic UIs and navigation based on the current URL.Example of
useLocation
in ReactSuppose you have a React application that uses
react-router-dom
for routing. Here's how you can use theuseLocation
hook to access and display the current pathname and search parameters in your component:First, make sure to install
react-router-dom
if you haven't already:npm install react-router-dom
Now, let's create a simple component that uses the
useLocation
hook:import React from 'react'; import { useLocation } from 'react-router-dom'; function CurrentLocation() { // Use the useLocation hook to access the current location object const location = useLocation(); return ( <div> <h2>Current Location Details:</h2> <p>Pathname: {location.pathname}</p> <p>Search Params: {location.search}</p> </div> ); } export default CurrentLocation;
In this example:
-
We import
useLocation
from'react-router-dom'
. -
Inside the
CurrentLocation
component, we use theuseLocation
hook to access the current location object, which contains information about the URL. -
We then display the current pathname and search parameters from the location object in the component.
Remember to use this component within a
Router
context provided byreact-router-dom
so that theuseLocation
hook can access the current route information. When the route changes, theCurrentLocation
component will automatically reflect the updated URL information.This is just a simple example, but you can use the
useLocation
hook to create more complex navigation and UI features based on the current URL in your React application. -
-
The
useHistory
hook is part of thereact-router-dom
library and provides a way to interact with the browser's history and navigate between routes programmatically in a React application. It's particularly useful for implementing dynamic navigation, redirecting users, and performing actions based on user interactions.Example of
useHistory
in ReactSuppose you have a simple React application that uses
react-router-dom
for routing. Here's how you can use theuseHistory
hook to programmatically navigate to different routes based on user interactions:First, ensure you have
react-router-dom
installed:npm install react-router-dom
Now, let's create a component that uses the
useHistory
hook:import React from 'react'; import { useHistory } from 'react-router-dom'; function NavigationExample() { // Use the useHistory hook to get access to the history object const history = useHistory(); const navigateToAbout = () => { // Programmatically navigate to the '/about' route history.push('/about'); }; const goBack = () => { // Navigate back in the browser's history history.goBack(); }; return ( <div> <h2>Navigation Example</h2> <button onClick={navigateToAbout}>Go to About</button> <button onClick={goBack}>Go Back</button> </div> ); } export default NavigationExample;
In this example:
-
We import
useHistory
from'react-router-dom'
. -
Inside the
NavigationExample
component, we use theuseHistory
hook to get access to thehistory
object. -
We define two functions:
navigateToAbout
andgoBack
. When the buttons are clicked, these functions use thehistory
object to perform navigation actions. -
navigateToAbout
useshistory.push('/about')
to programmatically navigate to the '/about' route. -
goBack
useshistory.goBack()
to navigate back in the browser's history stack.
Make sure that this component is used within a
Router
context provided byreact-router-dom
to access thehistory
object properly. TheuseHistory
hook allows you to create dynamic and interactive navigation elements in your React application. -
-
The
useParams
hook is part of thereact-router-dom
library and provides a way to access URL parameters defined in your routes. URL parameters are placeholders in your route patterns that can capture dynamic values from the URL and make them available in your components. This is useful for building components that rely on dynamic data from the URL.Example of
useParams
in ReactSuppose you have a React application with a route that includes a dynamic URL parameter, such as a product ID. You can use the
useParams
hook to access and use that parameter in your component:First, ensure you have
react-router-dom
installed:npm install react-router-dom
Now, let's create a component that uses the
useParams
hook:import React from 'react'; import { useParams } from 'react-router-dom'; function ProductDetail() { // Use the useParams hook to access URL parameters const { productId } = useParams(); return ( <div> <h2>Product Detail</h2> <p>Product ID: {productId}</p> </div> ); } export default ProductDetail;
In this example:
-
We import
useParams
from'react-router-dom'
. -
Inside the
ProductDetail
component, we use theuseParams
hook to access URL parameters. In this case, we're capturing theproductId
parameter from the URL. -
We display the value of the
productId
parameter in the component, allowing you to use it for data retrieval, rendering, or any other purpose.
To use this component and see it in action, you would define a route in your routing configuration that includes a dynamic URL parameter, like this:
import { BrowserRouter, Route, Switch } from 'react-router-dom'; function App() { return ( <BrowserRouter> <Switch> <Route path="/products/:productId"> <ProductDetail /> </Route> </Switch> </BrowserRouter> ); }
In this route configuration, the
:productId
part of the route pattern captures the dynamic product ID from the URL. TheProductDetail
component can then access and use this ID via theuseParams
hook.Using the
useParams
hook in combination with dynamic routes allows you to create components that adapt to different URL parameters and provide dynamic content based on the current route. -
-
In React 18's concurrent mode, the
useTransition
function is used to handle the transition between different render states. Concurrent mode allows React to work on multiple tasks concurrently, making applications more responsive and efficient.The
useTransition
function is typically used to wrap asynchronous operations, such as data fetching, to provide a smoother user experience. It helps manage the transition between loading and rendering data by allowing you to show loading indicators or placeholders while data is being fetched, and then smoothly transitioning to the actual data when it's ready.Example of
useTransition
in ReactHere's a conceptual example of how
useTransition
might be used in a React 18 application, although please note that this example does not reflect the actual API (as of my last update) but illustrates the concept:import React, { useTransition } from 'react'; function AsyncDataFetchingComponent() { const [startTransition, isPending] = useTransition(); const fetchData = async () => { startTransition(() => { // While fetching data, you can show a loading indicator or placeholder. // React will manage the transition smoothly. fetch('https://api.example.com/data') .then((response) => response.json()) .then((data) => { // Update the component state with the fetched data. // React will transition to displaying the data. }); }); }; return ( <div> <button onClick={fetchData}>Fetch Data</button> {isPending ? <LoadingIndicator /> : <DataDisplay />} </div> ); }
In this conceptual example:
-
We use the
useTransition
hook to start a transition. -
When fetching data, React can show a loading indicator (
LoadingIndicator
) while transitioning to the data display (DataDisplay
) when it's ready.
It's important to recognize that the example provided here is a simplified concept. In practice, utilizing
useTransition
and concurrent mode in React 18 may necessitate more intricate implementation and considerations. To ensure you are following the most current and effective practices, it is advisable to consult the latest React documentation and available resources. -
-
The
useDeferredValue
hook is designed to manage when a value is transitioned from being "deferred" to being "current." In React's concurrent mode, when you have expensive or non-urgent data or computations, you can defer their processing to avoid blocking the main thread. This can lead to a more responsive user interface.useDeferredValue
is often used in combination withuseTransition
. You can specify which data should be deferred and when it should become "current," allowing React to optimize the timing of rendering and transitions.Example of
useDeferredValue
in ReactHere's a simplified example of how
useDeferredValue
might be used, although it should be considered a conceptual representation:import React, { useDeferredValue, useTransition } from 'react'; function DeferredDataComponent() { const [isPending, startTransition] = useTransition(); // Simulate expensive data fetching (replace with actual asynchronous operation) const fetchData = async () => { startTransition(() => { // Deferring the processing of data const deferredData = someExpensiveDataProcessing(); // Declare which data should be deferred const deferredValue = useDeferredValue(deferredData); // React will optimize when to make deferredValue "current" // based on the rendering and transition priorities. }); }; return ( <div> <button onClick={fetchData}>Fetch Data</button> {isPending ? <LoadingIndicator /> : <DataDisplay />} </div> ); }
In this conceptual example:
-
We use
useDeferredValue
to indicate that thedeferredData
should be transitioned to a "current" state when it's appropriate according to React's concurrent mode logic. -
We use
useTransition
to manage the transition and indicate that some part of the rendering is pending. -
While data is being processed, we can show a loading indicator (
LoadingIndicator
) and transition smoothly to the data display (DataDisplay
) when the data becomes "current."
Please note that this example is a simplified illustration of the concept of
useDeferredValue
. The actual use and behavior ofuseDeferredValue
may be more complex and require consideration of concurrent mode principles. For the most accurate and up-to-date information onuseDeferredValue
and concurrent mode, refer to the latest React documentation and resources. -
-
A custom hook is a JavaScript function that uses built-in hooks or other custom hooks to manage and share stateful logic. Custom hooks are typically used to abstract complex behavior or state management so that it can be reused across multiple components. They follow a naming convention with the "use" prefix to indicate that they are hooks.
Custom hooks can be used for a variety of purposes, such as data fetching, form handling, managing local storage, or any other functionality that involves state or side effects. They help keep components clean and focused by extracting logic into separate, reusable functions.
Example of a Custom Hook
import { useState, useEffect } from 'react'; function useWindowDimensions() { const [windowDimensions, setWindowDimensions] = useState({ width: window.innerWidth, height: window.innerHeight, }); useEffect(() => { function handleResize() { setWindowDimensions({ width: window.innerWidth, height: window.innerHeight, }); } window.addEventListener('resize', handleResize); return () => { window.removeEventListener('resize', handleResize); }; }, []); return windowDimensions; } export default useWindowDimensions;
In this code:
-
We create a custom
useWindowDimensions
hook that usesuseState
to manage the window dimensions (width and height). -
We use
useEffect
to add a resize event listener that updates the window dimensions when the window is resized. -
The hook returns the current window dimensions.
By using this custom hook, you can access and respond to window dimensions in your components to create responsive and dynamic layouts.
-
The information provided in this GitHub repository, including articles, code examples, and documentation, is for educational and informational purposes only. It is intended to offer guidance and insights into working with React hooks and related technologies.
While every effort has been made to ensure the accuracy and reliability of the information provided, it should not be considered as professional advice or as a definitive source. Web development practices and technologies can change rapidly, and it's essential to verify and adapt information to your specific use case.
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Use the information in this repository at your own risk, and always seek professional guidance when necessary.