React 与 Web3 框架
将 React 等前端框架与 Web3 库集成，为 DApp 创建动态用户界面。
React 与 Web3 框架 是 CoddyKit 上的免费 Web3 & DApp Development Fundamentals 课时。 这是第 1 节课，共 3 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Web3 & DApp Development Fundamentals 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Web3 & DApp Development Fundamentals 课程共包含 3 节课。
本课时的部分内容尚未翻译，以英文显示。
DApps Need User Interfaces
Decentralized Applications (DApps) aren't just smart contracts running on a blockchain. Just like traditional apps, they need a user interface (UI) for people to interact with them.
This UI is what users see and click. It connects to their crypto wallet (like MetaMask) and communicates with the blockchain to display information or send transactions.
React for Dynamic UIs
React is a very popular JavaScript library for building modern user interfaces. It's known for its component-based architecture, where your UI is broken down into small, reusable pieces.
Using React helps developers create dynamic, responsive, and complex DApp front-ends more efficiently.
Web3 Libraries: The Blockchain Bridge
To make your React app talk to the Ethereum blockchain, you need a 'Web3 library'. These libraries act as a crucial bridge, translating your JavaScript code into blockchain-understandable commands.
- Web3.js: A comprehensive and widely used library for interacting with the Ethereum blockchain.
- Ethers.js: A modern, lightweight, and often preferred alternative to Web3.js, known for its clean API.
Setting Up a React Project
Let's start by creating a new React project. We'll use create-react-app, a common tool that sets up a new React application with a good default structure.
Open your terminal and run the following command:
npx create-react-app my-dapp-frontendInstalling a Web3 Library
After creating your React project and navigating into its directory, the next step is to install a Web3 library. For this lesson, we'll use Web3.js.
Run this command in your project's terminal:
npm install web3Connecting to an Ethereum Provider
Your DApp needs a connection to the Ethereum network. This connection is typically provided by the user's browser wallet, such as MetaMask. MetaMask injects a global window.ethereum object into the browser.
We use this window.ethereum object to initialize our Web3.js instance, allowing our app to read from and write to the blockchain.
Code Demo: Initialize Web3
This React component initializes Web3.js when the component mounts. It checks for a MetaMask provider and attempts to connect, updating the UI based on the connection status.
import React, { useEffect, useState } from 'react';
import Web3 from 'web3';
function App() {
const [web3, setWeb3] = useState(null);
const [isConnected, setIsConnected] = useState(false);
useEffect(() => {
const initWeb3 = async () => {
if (window.ethereum) {
try {
// Request account access
await window.ethereum.request({ method: 'eth_requestAccounts' });
const web3Instance = new Web3(window.ethereum);
setWeb3(web3Instance);
setIsConnected(true);
console.log('Web3 connected!');
} catch (error) {
console.error('User denied or connection error:', error);
}
} else {
console.log('MetaMask not detected. Install it!');
}
};
initWeb3();
}, []); // Runs once on component mount
return (
<div>
<h1>DApp Frontend</h1>
{isConnected ? (
<p>Connected to Ethereum!</p>
) : (
<p>Not connected. Please install MetaMask.</p>
)}
</div>
);
}
export default App;Fetching User Account Address
Once connected to the Ethereum provider, we can use our web3 instance to retrieve the user's connected wallet addresses. This is a fundamental step for any DApp that needs to display user-specific data or prepare for transactions.
We typically fetch the first account from the list returned by web3.eth.getAccounts().
Displaying Account in React State
To show the connected account address in our React application, we'll store it in React's state using the useState hook. This allows the UI to automatically update when the account is fetched.
Let's update our App.js to display the connected account:
import React, { useEffect, useState } from 'react';
import Web3 from 'web3';
function App() {
const [web3, setWeb3] = useState(null);
const [account, setAccount] = useState(null);
const [isConnected, setIsConnected] = useState(false);
useEffect(() => {
const initWeb3 = async () => {
if (window.ethereum) {
try {
await window.ethereum.request({ method: 'eth_requestAccounts' });
const web3Instance = new Web3(window.ethereum);
setWeb3(web3Instance);
setIsConnected(true);
const accounts = await web3Instance.eth.getAccounts();
setAccount(accounts[0]); // Store the first account
console.log('Connected account:', accounts[0]);
} catch (error) {
console.error('Connection error:', error);
setAccount(null);
setIsConnected(false);
}
} else {
console.log('MetaMask not detected.');
setAccount(null);
setIsConnected(false);
}
};
initWeb3();
}, []); // Empty dependency array means this runs once on mount
return (
<div>
<h1>My DApp</h1>
{isConnected && account ? (
<p>Connected account: <code>{account}</code></p>
) : (
<p>Please connect your wallet.</p>
)}
</div>
);
}
export default App;Web3 Integration Check
Which of the following is the primary purpose of a Web3 library (like Web3.js or Ethers.js) in a React DApp?
Integrating React & Web3 Recap
Today, we took our first steps into building DApp front-ends! We learned that React is excellent for building dynamic UIs, and Web3 libraries like Web3.js are crucial for connecting these UIs to the Ethereum blockchain.
We covered how to set up a React project, install Web3.js, initialize a connection using the window.ethereum provider, and fetch the user's connected wallet address to display in our app.
This foundational knowledge is key to making your DApps interactive and user-friendly. Next, we'll dive deeper into handling wallet connections and transactions.
常见问题解答
「React 与 Web3 框架」课时是免费的吗？
是的 — 「React 与 Web3 框架」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Web3 & DApp Development Fundamentals 课程的其余内容，请升级到 CoddyKit PRO。 Web3 & DApp Development Fundamentals 课程共包含 3 节课。
「React 与 Web3 框架」这节课中我会学到什么？
将 React 等前端框架与 Web3 库集成，为 DApp 创建动态用户界面。 你通过在浏览器中直接运行的动手代码来练习 Web3 & DApp Development Fundamentals，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Web3 & DApp Development Fundamentals 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Web3 & DApp Development Fundamentals 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 1 节课，共 3 节。
「React 与 Web3 框架」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Web3 & DApp Development Fundamentals 课中编写并运行代码吗？
能。每节 Web3 & DApp Development Fundamentals 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。