webpack配置

webpack核心概念:

入口(entry) 指定webpack开始构建的入口模块，从该模块开始构建并计算出直接或间接依赖的模块或者库
输出(output)告诉webpack如何命名输出的文件以及输出的目录
path ：入口文件最终要输出到哪里，
filename：输出文件的名称
publicPath：公共资源路径
loader 由于webpack只能处理javascript，所以我们需要对一些非js文件处理成webpack能够处理的模块，比如sass文件
插件(plugins)
-chunkcoding split的产物，我们可以对一些代码打包成一个单独的chunk，比如某些公共模块，去重，更好的利用缓存。或者按需加载某些功能模块，优化加载时间。在webpack3及以前我们都利用CommonsChunkPlugin将一些公共代码分割成一个chunk，实现单独加载。在webpack4 中CommonsChunkPlugin被废弃，使用SplitChunksPlugin

webpack安装流程

step1:首先安装Node.js
step2:通过全局先将webpack指令安装进电脑中npm install webpack -g npm install --save-dev webpack
step3:npm init(会生成一个package.json的文件)

webpack配置

step1: 创建项目文件夹, 例如webpack_test
step2: 在你的项目目录下创建webpack.config.js配置文件, 通过这个文件进行webpack的配置, 并且还要创建一些路径保存基本文件,例如创建一个src文件夹，里面分别创建js,css,img文件夹
step3：在src的js下创建一个入口文件, 我创建的叫做entry.js, 在项目目录再创建一个index.html用来调试使用. 编写webpack.config.js文件,

//webpack.config.js
module.exports = {
    entry : './src/js/entry.js',//入口文件
    output : {//输出文件
        filename : 'index.js',//输出文件名
        path : __dirname + '/out'//输出文件路径
    },
}

index.html和入口文件entry.js

//index.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8" />
    <title>ss</title>
</head>
<body>
111
    <script src="./out/index.js"></script>//注意在这里引入的是打包完成的js文件
</body>
</html>

//entry.js
console.log('1234');

webpack loader加载器

npm install babel-loader babel babel-core css-loader style-loader  url-loader file-loader less-loader less  --save-dev

修改webpack.config.js文件

module.exports = {
    entry :  './src/js/entry.js',
    output : {
        filename : 'index.js',
        path : __dirname + '/out'
    },
    module : {
        rules: [
            {test: /.js$/, use: ['babel-loader']},
            {test: /.css$/, use: ['style-loader', 'css-loader']},/*解析css, 并把css添加到html的style标签里*/
            //{test: /.css$/, use: ExtractTextPlugin.extract({fallback: 'style-loader',use: 'css-loader'})},/*解析css, 并把css变成文件通过link标签引入*/
            {test: /.(jpg|png|gif|svg)$/, use: ['url-loader?limit=8192&name=./[name].[ext]']},/*解析图片*/
            {test: /.less$/, use: ['style-loader', 'css-loader', 'less-loader']}/*解析less, 把less解析成浏览器可以识别的css语言*/
        ]
    },
    }

webpack插件使用

修改webpack.config.js

var webpack = require('webpack');
var webpack = require('webpack');
var uglifyPlugin = new webpack.optimize.UglifyJsPlugin({minimize: true});//代码压缩

var CommonsChunkPlugin = new webpack.optimize.CommonsChunkPlugin('common');//把公共模块提取出来, 并取名为'common'(名字自起), webpack之后再out文件夹下生成common.js, 测试时记得引入提取出来的公共模块js文件

var ExtractTextPlugin = require("extract-text-webpack-plugin");//将css独立引入变成link标签形式, 使用该插件需要独立下载'npm install extract-text-webpack-plugin --save-dev', 同时下面的rules也必须更改

var providePlugin = new webpack.ProvidePlugin({$: 'jquery', jQuery: 'jquery', 'window.jQuery': 'jquery'});//引入jquery



module.exports = {
    entry : {index: './src/js/entry.js', index2: './src/js/entry2.js'},
    output : {
        filename : '[name].js',
        publicPath: __dirname + '/out',
        path : __dirname + '/out'
    },
    module : {
        rules: [
            {test: /.js$/, use: ['babel-loader']},
            //{test: /.css$/, use: ['style-loader', 'css-loader']},
            {test: /.css$/, use: ExtractTextPlugin.extract({fallback: 'style-loader',use: 'css-loader'})},
            {test: /.(jpg|png|gif|svg)$/, use: ['url-loader?limit=8192&name=./[name].[ext]']},
            {test: /.less$/, use: ['style-loader', 'css-loader', 'less-loader']}
        ]
    },
    plugins: [uglifyPlugin, CommonsChunkPlugin, new ExtractTextPlugin('[name].css'),providePlugin]//插件集合
}

webpack服务器

首先先定位目录输入命令 npm install webpack-dev-server -g, 修改webpack.config.js文件

publicPath: 'http://localhost:8080/out',

package.json

{
  "name": "pmall",
  "version": "4.2.6",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "cross-env NODE_ENV=development webpack-dev-server --open --port 4000 --hot --host 0.0.0.0 --content-base ./build --config ./build/webpack.config.dev.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "vue": "^2.5.3"
  },
  "devDependencies": {
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.2",
    "babel-plugin-transform-runtime": "^6.23.0",
    "babel-preset-es2015": "^6.24.1",
    "babel-preset-stage-0": "^6.24.1",
    "babel-preset-stage-2": "^6.24.1",
    "babel-runtime": "^6.26.0",
    "cross-env": "^5.1.1",
    "css-loader": "^0.28.7",
    "extract-text-webpack-plugin": "^3.0.2",
    "file-loader": "^1.1.5",
    "html-loader": "^0.5.1",
    "html-webpack-plugin": "^2.30.1",
    "node-sass": "^4.6.0",
    "postcss-loader": "^2.0.9",
    "sass-loader": "^6.0.6",
    "style-loader": "^0.19.0",
    "uglifyjs-webpack-plugin": "^1.0.1",
    "url-loader": "^0.6.2",
    "vue-loader": "^13.4.0",
    "vue-router": "^3.0.1",
    "vue-template-compiler": "^2.5.3",
    "webpack": "^3.8.1",
    "webpack-dev-server": "^2.9.4"
  },
  "description": ""
}