react项目自行配置热更新

react项目自己配置热更新的话需要安装两个包@pmmmwh/react-refresh-webpack-plugin和react-refresh，这个是官方推荐的做法。下面给出一个完整demo

App.js

import React, { useState } from "react";function App() {const [count, setCount] = useState(0);return (<div><h1 onClick={() => setCount(count + 1)}>{count}</h1><div>1</div></div>);
}export default App;

index.html

<!DOCTYPE html>
<html lang="zn"><head><meta charset="UTF-8" /><meta name="viewport" content="width=device-width, initial-scale=1.0" /><title>React App</title></head><body><div id="app"></div></body>
</html>

index.js

import React from "react";
import App from "./App";
import { createRoot } from "react-dom/client";
const root = createRoot(document.getElementById("app"));root.render(<App></App>);

webpack.config.js

const ReactRefreshPlugin = require("@pmmmwh/react-refresh-webpack-plugin");
const HtmlWebpackPlugin = require("html-webpack-plugin");module.exports = {entry: "./index.js",mode: "development",devServer: {static: "./dist",hot: true,},module: {rules: [{test: /\.js$/,exclude: /node_modules/,loader: "babel-loader",options: {presets: ["@babel/env", "@babel/preset-react"],plugins: [require.resolve("react-refresh/babel")], // react-refresh 添加},},],},plugins: [new ReactRefreshPlugin(),new HtmlWebpackPlugin({template: "./index.html",}),],
};

package.json

{"name": "react-hmr","version": "0.1.0","private": true,"scripts": {"start": "webpack-dev-server"},"dependencies": {"@babel/core": "^7.23.3","@babel/preset-env": "^7.23.3","@babel/preset-react": "^7.23.3","@pmmmwh/react-refresh-webpack-plugin": "^0.5.11","babel-loader": "^9.1.3","html-webpack-plugin": "^5.5.3","react": "^18.2.0","react-dom": "^18.2.0","react-refresh": "^0.14.0","webpack": "^5.89.0","webpack-cli": "^5.1.4","webpack-dev-server": "^4.15.1"}
}

之后执行npm start，大家自行测试

这里说一下注意点，每个组件只能使用一个export，如果有多个，热更新会失效，这点很重要。例如我们修改App.js

App.js

import React, { useState } from "react";export const delay = () => {}function App() {const [count, setCount] = useState(0);return (<div><h1 onClick={() => setCount(count + 1)}>{count}</h1><div>1</div></div>);
}export default App;

这里多加了一个export const delay，大家可以试一下。这个时候热更新就不起作用了。

这里还解释一下为什么不用webpack的hmr，webpack不是自带hmr么，为什么还安装其他的包呢？这个问题大家可以看一下我这篇文章

还有一种方式是使用react-hot-loader，不过react-hot-loader已经不推荐使用了。

我们这里基于上面的代码进行改编，这里react和react-dom需要降级，把18版本降级成17版本。不然无法使用。先执行

npm i react@17.0.0 react-dom@17.0.0
npm i react-hot-loader

修改webpack.config.js配置

const HtmlWebpackPlugin = require("html-webpack-plugin");module.exports = {entry: "./index.js",mode: "development",devServer: {static: "./dist",hot: true,},module: {rules: [{test: /\.js$/,exclude: /node_modules/,loader: "babel-loader",options: {presets: ["@babel/env", "@babel/preset-react"],plugins: ["react-hot-loader/babel"],},},],},plugins: [new HtmlWebpackPlugin({template: "./index.html",}),],
};

修改index.js

import { hot } from "react-hot-loader/root";
import React from "react";
import App from "./App";
import { render } from "react-dom";const HotComponent = hot(App);render(<HotComponent />, document.getElementById("app"));if (module.hot) {module.hot.accept("./App", () => {render(<HotComponent />, document.getElementById("app"));});
}