详解webpack2+node+react+babel实现热加载(hmr)

前端工程化开发的一个重要标志就是热替换技术，它大大的提高开发效率，使我们专注于写代码，webpack2中的热替换相比较1更加简洁。

1. 先看效果

2.目录结构

3.项目目录结构文件描述

bin 执行文件

node_modules node包

public 静态资源文件

• static 静态资源
• dist 编译后文件

src 项目js文件

.bablrc babel配置文件

webpack.config.dev.js开发模式webpack配置

webpack.config.pro.js生产模式webpack配置

3.技术依赖

• node
• react
• babel
• ES6/ES2015
• react-hmre
• webpack

babel-loader,css-loader,sass-loader,style-loader,webpack-hot-middleware,webpack-hot-middleware

热加载最重要的几个配置是packge.json/devserver.js/webpack.config.dev.js/webpack.config.prod.js/.babelrc

packge.json

{
 "name": "react-hmr-demo",
 "version": "1.0.0",
 "description": "react-hmr-demo",
 "main": "index.js",
 "scripts": {
  "dev": "node bin/devserver.js",
  "build":" webpack --config webpack.config.prod.js ",
  "start":"node bin/server.js"
 },
 "repository": {
  "type": "git",
  "url": "git+https://github.com/leinov/react-hmr-demo.git"
 },
 "author": "leinov",
 "license": "ISC",
 "dependencies": {
  "express": "^4.15.4",
  "react": "^15.6.1",
  "react-dom": "^15.6.1"
 },
 "devDependencies": {
  "babel-core": "^6.26.0",
  "babel-loader": "^7.1.2",
  "babel-polyfill": "^6.26.0",
  "babel-preset-es2015": "^6.24.1",
  "babel-preset-react": "^6.24.1",
  "babel-preset-react-hmre": "^1.1.1",
  "css-loader": "^0.28.5",
  "eventsource-polyfill": "^0.9.6",
  "node-sass": "^4.5.3",
  "sass-loader": "^6.0.6",
  "style-loader": "^0.18.2",
  "webpack": "^3.5.5",
  "webpack-dev-middleware": "^1.12.0",
  "webpack-hot-middleware": "^2.18.2"
 }
}

scripts的几个命令

$ npm run dev //开发模式
$ npm run build //编译打包
npm start //正式环境运行

webpack.config.dev.js

var path = require('path');
var webpack = require('webpack');

module.exports = {

  devtool: 'cheap-module-eval-source-map',//打包构建信息

  entry: [

    'eventsource-polyfill',//for IE
    'webpack-hot-middleware/client',//webpack服务连接到浏览器接收更新

    './src/index.js'
  ],

  output: {
    filename: 'boundle.js',
    publicPath: '/dist/js/'
  },

  module: {

    loaders: [{
        test: /\.js$/,
        loaders: ['babel-loader'],
        exclude: /node_modules/ //哪些文件下的需要用到babel
      }, {
        test: /\.css$/,
        loaders: ['style-loader', 'css-loader'],
      },
      {
        test: /\.scss$/,
        loaders: ['style-loader', 'css-loader', 'sass-loader'],
      },
      {
        test: /\.(png|jpg|gif)$/,
        loaders: ['url?limit=8192&name=images/[name].[ext]'],
      }
    ]
  } ,

  resolve:{

    alias: {

      css: path.resolve(__dirname, 'public/static/css/'), //css目录别名
    }
  },

  plugins: [

    new webpack.HotModuleReplacementPlugin(),//热替换插件
    new webpack.NoEmitOnErrorsPlugin()
  ]
};

.babelrc

{
 "presets": ["react", "es2015"]，
 "env": {
    "development": {

      "presets": ["react-hmre"]
    }
 }
}

devserver.js

var path = require('path');
var express = require('express');
var webpack = require('webpack');
var config = require('../webpack.config.dev');

var app = express();
var compiler = webpack(config);

var webpackDevMiddleware = require("webpack-dev-middleware");

app.use(webpackDevMiddleware(compiler, {

  noInfo: false, //true将打印编译信息（建议false，true会打印很多信息）
  publicPath: config.output.publicPath //绑定middleware
}));

var webpackHotMiddleware = require('webpack-hot-middleware');
app.use(webpackHotMiddleware(compiler));

app.get('*', function(req, res) {

  res.sendFile(path.resolve(__dirname, '../index.html')); //
});

app.listen(3100, function(err) {

  if (err) {
    console.log(err);
    return;
  }
  console.log('Listening at http://localhost:3100');
});

这样就可以实现热加载了，在项目根目录执行

$ npm run dev

webpack.config.prod.js

var path = require('path');
var webpack = require('webpack');

module.exports = {
  devtool: 'cheap-module-eval-source-map',
  entry: [
    './src/index.js'
  ],
  output: {

    path: path.join(__dirname, 'public/dist/js'),
    filename: 'boundle.js',

  },
  module: {

    loaders: [{
        test: /\.js$/,
        loaders: ['babel-loader'],
        exclude: /node_modules/
      }, {
        test: /\.css$/,
        loaders: ['style-loader', 'css-loader'],
      },
      {
        test: /\.scss$/,
        loaders: ['style-loader', 'css-loader', 'sass-loader'],
      },
      {
        test: /\.(png|jpg|gif)$/,
        loaders: ['url?limit=8192&name=images/[name].[ext]'],
      }
    ]
  } ,
  resolve:{
    alias: {
      css: path.resolve(__dirname, 'public/static/css/'),
      img: path.resolve(__dirname, 'public/static/img/'),
    }
  },

  plugins: [

     new webpack.HotModuleReplacementPlugin(),
     new webpack.NoEmitOnErrorsPlugin(),
     new webpack.optimize.UglifyJsPlugin({
         compress: {
          warnings: false
        }
      })

    ]
  };

生产的webpack主要完成开发后的编译打包，在plugins里多了压缩插件,在项目根目录执行

$ npm run build

bin/server.js

生产环境启动文件

var path = require('path');
var express = require('express');
var app = express();

var oneYear = 60 * 1000 * 60 * 24 * 30;

app.use(express.static(path.resolve(__dirname, '../public'), { maxAge: oneYear }));

app.get('*', function(req, res) {

  res.sendFile(path.resolve(__dirname,'../index.html'));
});

app.listen(3200, function(err) {

  if (err) {
    console.log(err);
    return;
  }
 console.log('Listening at http://localhost:3200');

});

$ npm start //运行生产环境

这里是项目地址 https://github.com/leinov/react-hmr-demo

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