webpack基本用法

1.安装webpack 

//全局安装
npm install -g webpack
//安装到你的项目目录
npm install --save-dev webpack

2.编写webpack配置文件

webpack.config.js

var webpack=require('webpack');
const path=require('path');
const htmlWebpackPlugin=require('html-webpack-plugin');


module.exports={
    entry:'./main.js',
    output:{
        path: path.resolve(__dirname + '/dist'),
        filename:'main.bundle.js'
    },
    devServer:{
        contentBase:'./dist'
    },
    plugins:[
    
        new htmlWebpackPlugin({
            title:'output html',
            template:'index.html'
        })
    ]
}

3.执行webpack命令

4.使用 webpack-dev-server

webpack-dev-server 为你提供了一个简单的 web 服务器，并且能够实时重新加载(live reloading)。让我们设置以下：

npm install --save-dev webpack-dev-server

修改配置文件，告诉开发服务器(dev server)，在哪里查找文件：

webpack.config.js

  const path = require('path');
  const HtmlWebpackPlugin = require('html-webpack-plugin');
  const CleanWebpackPlugin = require('clean-webpack-plugin');

  module.exports = {
    entry: {
      app: './src/index.js',
      print: './src/print.js'
    },
    devtool: 'inline-source-map',
+   devServer: {
+     contentBase: './dist'
+   },
    plugins: [
      new CleanWebpackPlugin(['dist']),
      new HtmlWebpackPlugin({
        title: 'Development'
      })
    ],
    output: {
      filename: '[name].bundle.js',
      path: path.resolve(__dirname, 'dist')
    }
  };

以上配置告知 webpack-dev-server，在 localhost:8080 下建立服务，将 dist 目录下的文件，作为可访问文件。

让我们添加一个 script 脚本，可以直接运行开发服务器(dev server)：

package.json

  {
    "name": "development",
    "version": "1.0.0",
    "description": "",
    "main": "webpack.config.js",
    "scripts": {
      "test": "echo "Error: no test specified" && exit 1",
      "watch": "webpack --progress --watch",
+     "start": "webpack-dev-server --open",
      "build": "webpack"
    },
    "keywords": [],
    "author": "",
    "license": "ISC",
    "devDependencies": {
      "clean-webpack-plugin": "^0.1.16",
      "css-loader": "^0.28.4",
      "csv-loader": "^2.1.1",
      "file-loader": "^0.11.2",
      "html-webpack-plugin": "^2.29.0",
      "style-loader": "^0.18.2",
      "webpack": "^3.0.0",
      "xml-loader": "^1.2.1"
    }
  }

现在，我们可以在命令行中运行 npm start，就会看到浏览器自动加载页面。如果现在修改和保存任意源文件，web 服务器就会自动重新加载编译后的代码。

注意：使用 webpack-dev-server命令时，项目中不会有dist目录。它是被写在内存中。直接使用webpack命令时才会有dist目录。

 

5.使用 webpack-dev-middleware

webpack-dev-middleware 是一个中间件容器(wrapper)，它将通过 webpack 处理后的文件发布到一个服务器(server)。在内部 webpack-dev-server 它使用，然而，它可以作为一个单独的包来提供，可以进行更多的自定义设置来实现更多需求。接下来是一个 webpack-dev-middleware 配合 express server 的示例。

首先，安装 express 和 webpack-dev-middleware：

npm install --save-dev express webpack-dev-middleware

接下来我们需要对 webpack 的配置文件做一些调整，以确保中间件(middleware)功能能够正确启用：

webpack.config.js

  const path = require('path');
  const HtmlWebpackPlugin = require('html-webpack-plugin');
  const CleanWebpackPlugin = require('clean-webpack-plugin');

  module.exports = {
    entry: {
      app: './src/index.js',
      print: './src/print.js'
    },
    devtool: 'inline-source-map',
    plugins: [
      new CleanWebpackPlugin(['dist']),
      new HtmlWebpackPlugin({
        title: 'Output Management'
      })
    ],
    output: {
      filename: '[name].bundle.js',
      path: path.resolve(__dirname, 'dist'),
+     publicPath: '/'
    }
  };

publicPath 也会在服务器脚本用到，以确保文件资源能够在 http://localhost:3000 下正确访问，我们稍后再设置端口号。下一步就是设置我们自定义的 express 服务：

project

  webpack-demo
  |- package.json
  |- webpack.config.js
+ |- server.js
  |- /dist
  |- /src
    |- index.js
    |- print.js
  |- /node_modules
server.js

const express = require('express');
const webpack = require('webpack');
const webpackDevMiddleware = require('webpack-dev-middleware');

const app = express();
const config = require('./webpack.config.js');
const compiler = webpack(config);

// Tell express to use the webpack-dev-middleware and use the webpack.config.js
// configuration file as a base.
app.use(webpackDevMiddleware(compiler, {
  publicPath: config.output.publicPath
}));

// Serve the files on port 3000.
app.listen(3000, function () {
  console.log('Example app listening on port 3000!
');

6.启用 HMR（使用webpack-dev-server方式）

webpack.config.js
  const path = require('path');
  const HtmlWebpackPlugin = require('html-webpack-plugin');
  const CleanWebpackPlugin = require('clean-webpack-plugin');
+ const webpack = require('webpack');

  module.exports = {
    entry: {
-      app: './src/index.js',
-      print: './src/print.js'
+      app: './src/index.js'
    },
    devtool: 'inline-source-map',
    devServer: {
      contentBase: './dist',
+     hot: true
    },
    plugins: [
      new CleanWebpackPlugin(['dist']),
      new HtmlWebpackPlugin({
        title: 'Hot Module Replacement'
      }),
+     new webpack.NamedModulesPlugin(),
+     new webpack.HotModuleReplacementPlugin()
    ],
    output: {
      filename: '[name].bundle.js',
      path: path.resolve(__dirname, 'dist')
    }
  };

你可以通过命令来修改 webpack-dev-server 的配置：webpack-dev-server --hot-only。

注意，我们还添加了 NamedModulesPlugin，以便更容易查看要修补(patch)的依赖。在起步阶段，我们将通过在命令行中运行 npm start 来启动并运行 dev server。

按照上述方法进行模块热替换，更改文件后虽然执行了热替换，但是页面并没有自动刷新，具体原因不详。

通过 Node.js API

当使用 webpack dev server 和 Node.js API 时，不要将 dev server 选项放在 webpack 配置对象(webpack config object)中。而是，在创建选项时，将其作为第二个参数传递。例如：

new WebpackDevServer(compiler, options)

想要启用 HMR，还需要修改 webpack 配置对象，使其包含 HMR 入口起点。webpack-dev-server package 中具有一个叫做 addDevServerEntrypoints 的方法，你可以通过使用这个方法来实现。这是关于如何使用的一个小例子：

dev-server.js
const webpackDevServer = require('webpack-dev-server');
const webpack = require('webpack');

const config = require('./webpack.config.js');
const options = {
  contentBase: './dist',
  hot: true,
  host: 'localhost'
};

webpackDevServer.addDevServerEntrypoints(config, options);
const compiler = webpack(config);
const server = new webpackDevServer(compiler, options);

server.listen(5000, 'localhost', () => {
  console.log('dev server listening on port 5000');
});

 7.使用webpack-dev-middleware和webpack-hot-middleware(可以热替换和与express结合，实现服务监听和自动刷新页面)

npm install --save-dev webpack-hot-middleware

修改配置文件：

1.配置文件添加：
plugins: [
    // OccurenceOrderPlugin is needed for webpack 1.x only
    new webpack.optimize.OccurenceOrderPlugin(),
    new webpack.HotModuleReplacementPlugin(),
    // Use NoErrorsPlugin for webpack 1.x
    new webpack.NoEmitOnErrorsPlugin()
]
2.服务器文件添加：
var webpack = require('webpack');
var webpackConfig = require('./webpack.config');
var compiler = webpack(webpackConfig);

app.use(require("webpack-dev-middleware")(compiler, {
    noInfo: true, publicPath: webpackConfig.output.publicPath
}));
app.use(require("webpack-hot-middleware")(compiler));
3.要实现自动刷新还要添加：
var ansiColors = {
red: '00FF00' // note the lack of "#"
};
var overlayStyles = {
color: '#FF0000' // note the inclusion of "#" (these options would be the equivalent of div.style[option] = value)
};
var hotMiddlewareScript = 'webpack-hot-middleware/client?path=/__webpack_hmr&timeout=20000&reload=true&ansiColors=' + encodeURIComponent(JSON.stringify(ansiColors)) + '&overlayStyles=' + encodeURIComponent(JSON.stringify(overlayStyles));

4.完整的配置文件：

var webpack=require('webpack');
const path=require('path');
const htmlWebpackPlugin=require('html-webpack-plugin');


var ansiColors = {
  red: '00FF00' // note the lack of "#"
};
var overlayStyles = {
  color: '#FF0000' // note the inclusion of "#" (these options would be the equivalent of div.style[option] = value)
};
var hotMiddlewareScript = 'webpack-hot-middleware/client?path=/__webpack_hmr&timeout=20000&reload=true&ansiColors=' + encodeURIComponent(JSON.stringify(ansiColors)) + '&overlayStyles=' + encodeURIComponent(JSON.stringify(overlayStyles));
module.exports={
    entry:['./public/javascripts/main.js',hotMiddlewareScript],
    output:{
        path:path.resolve(__dirname,'dist'),
        filename:'main.bundle.js',
        publicPath:'/'
    },
    devServer:{
        contentBase:'./dist'
    },
    plugins:[
    
        new htmlWebpackPlugin({
            title:'output html',
            template:'index.html'
        }),
         // OccurenceOrderPlugin is needed for webpack 1.x only
   
    new webpack.HotModuleReplacementPlugin(),
    // Use NoErrorsPlugin for webpack 1.x
    new webpack.NoEmitOnErrorsPlugin()
    ]
}