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

javascript 复制代码

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

html 复制代码

<!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

javascript 复制代码

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

javascript 复制代码

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

json 复制代码

{
  "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

javascript 复制代码

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

javascript 复制代码

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

javascript 复制代码

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"));
  });
}