服务端渲染 react

1. 服务端渲染的好处

SEO和首屏时间

2. 热替换

react-hot-reload（react-hot-reload不用刷新浏览器）, (webpack-dev-server还是需要刷新浏览器)

3. 速成的代码

1). 分成client端， 借用webpack打包到dist下面。 将用于生成string的html加入替换的标记<!--app-->

2). 服务端node, 借助webpack(target:node), 生成压缩版的组件，读取导出的客户端组件； 然后读取index.html， 替换<!--app-->

3).。 调用renderToString(App)， 返回string.

server.js

const express = require("express");
const path = require("path");
const React = require("react");
const { renderToString } = require("react-dom/server");
const { readFile: rf } = require("fs");
const { promisify } = require("util");
// const App = require("../client/app").default;
const App = require('../../dist/serverapp.js').default

const app = express();
const readFile = promisify(rf);

app.use(express.json());
app.use(express.urlencoded({ extended: false }));
const text = renderToString(App);
console.log(text);
app.get("/",async (req,res) => {
    const content = renderToString(App);
    // 读取打包出来的 HTML 文件
    const str = await readFile(path.join(__dirname, "../../dist/index.html"));
    // 把内容替换掉
    const html = str.toString().replace("<!--app-->",content);
    // 将页面发到前端
    res.send(html);
});
// 打包生成的文件夹作为静态服务路径，这样静态文件就可以请求到了
app.use("/test",express.static(path.join(__dirname, "../../dist")));

app.listen(8001,() => {
    console.log("Server is running: http://localhost:8001");
});

　server->webpack.js

const path = require("path");

module.exports = {
    target:"node",
  entry: path.join(__dirname, "./src/client/server-app.js"),
  output: {
    path: path.join(__dirname, "./dist"),
    filename: "serverapp.js",
    libraryTarget: "commonjs2"
  },
  mode: "development", //production慢
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader",
        },
      },
    ],
  },
  resolve: {
    extensions: [".js", ".jsx", ".mjs"],
  },
  plugins: []
};

client: webpackl

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const { CleanWebpackPlugin } = require("clean-webpack-plugin");

module.exports = {
  entry: path.join(__dirname, "./src/client/index.js"),
  output: {
    path: path.join(__dirname, "./dist"),
    filename: "bundle.js",
  },
  mode: "development", //production慢
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader",
        },
      },
    ],
  },
  resolve: {
    extensions: [".js", ".jsx", ".mjs"],
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: path.join(__dirname, "./src/client/index.html"),
    }),
    new CleanWebpackPlugin({
      cleanOnceBeforeBuildPatterns: ["./dist"],
      dry: false,
      dangerouslyAllowCleanPatternsOutsideProject: true,
    }),
  ],
  devServer: {
    hot:true,
    host: 'localhost',
    compress: true,
    port: 8080
  }
};