获取全套webpack 4.x教程，请访问瓦力博客
在上一小节，我们将开发环境和生产环境区分开来。这一小节，我们来操作如何将样式文件的代码分割。
- MiniCssExtractPlugin{:target="_blank"}
1.安装
yarn add mini-css-extract-plugin
此插件将CSS提取到单独的文件中。它为每个包含CSS的JS文件创建一个CSS文件。它支持CSS和SourceMaps的按需加载。
它建立在新的webpack v4功能（模块类型）之上，并且需要webpack 4才能工作。
注意:MiniCssExtractPlugin 目前不支持HMR support(热重载)
2.提取css
bulid/plugins.js
const srcPath = require('./base/path');
const config = require('./base/config');
const webpack = require('webpack');
const HtmlWebpackPlugin = require('html-webpack-plugin'); //生成html文件
const { CleanWebpackPlugin } = require('clean-webpack-plugin'); //清除
+ const MiniCssExtractPlugin = require("mini-css-extract-plugin"); //css样式提取
let plugins = [
new HtmlWebpackPlugin({
title: '瓦力博客',
template: srcPath.src + '/index.html' //以src/index.html为编译模板
}),
+ new MiniCssExtractPlugin({
+ filename: config.NODE_ENV == 'development'?'[name.css]': `${srcPath.css}/[name].[hash].css`,
+ chunkFilename: config.NODE_ENV == 'development'?'[id].css': `${srcPath.css}/[id].[hash].css`
+ }), //css提取
new CleanWebpackPlugin(),
new webpack.HotModuleReplacementPlugin()
]
module.exports = plugins;
build/module.js
const srcPath = require('./base/path');
const config = require('./base/config');
+ const MiniCssExtractPlugin = require("mini-css-extract-plugin");
let _module = {
rules:[
{
test:/\.css$/,
use:[
+ config.NODE_ENV == 'development'?'style-loader': MiniCssExtractPlugin.loader,
{
loader:'css-loader',
options:{
importLoaders:1
}
},
'postcss-loader'
]
},
{
test:/\.scss$/,
use:[
+ config.NODE_ENV == 'development'?'style-loader': MiniCssExtractPlugin.loader,
{
loader:'css-loader',
options:{
importLoaders:2
}
},
'sass-loader',
'postcss-loader'
]
},
{
test: /\.less$/,
use: [
+ config.NODE_ENV == 'development'?'style-loader': MiniCssExtractPlugin.loader,
{
loader:'css-loader',
options:{
importLoaders:2
}
},
'less-loader',
'postcss-loader'
]
},
{
test:/\.(png|svg|jpeg|jpg|gif)$/,
use:[
{
loader:'file-loader',
options:{
name:'[name][sha512:hash:base64:7].[ext]', //[path] 上下文环境路径
outputPath: srcPath.images, //输出路径
publicPath: config.NODE_ENV === 'development'?srcPath.images:srcPath.images //公共路径
}
},
{
loader: 'image-webpack-loader',
options: {
bypassOnDebug: true, // webpack@1.x
disable: true, // webpack@2.x and newer
},
},
]
},
{
test: /\.html$/,
use:[
{
loader:'html-loader',
options:{
arrts:['img:src','img:data-src'],
+ minimize:config.NODE_ENV === 'development'? false:false //是否压缩html
}
}
]
},
{
test: /(iconfont.svg)|\.(woff|woff2|eot|ttf|otf)$/,
use:[
{
loader:'file-loader',
options:{
name:'[name].[ext]', //[path] 上下文环境路径
outputPath: srcPath.iconfont, //输出路径
publicPath: config.NODE_ENV === 'development'? srcPath.iconfont: srcPath.iconfont, //公共路径
}
}
]
},
{
test: /\.js$/,
exclude: /(node_modules|bower_components|lib)/,
loader: 'babel-loader'
}
]
}
module.exports = _module;
build/base/config.js
let _mode = process.argv[process.argv.length - 1];
let env = _mode.replace(/--mode=(.+)/g,"$1");
let config = {
NODE_ENV: env == 'development'?'development':'production', //development 开发 production 线上
+ publicPath: env == 'development'?'./':'./',
apiUrl:'http://www.waliblog.com',
port: 9999
}
module.exports = config;
package.json
{
"name": "webpack",
"version": "1.0.0",
"description": "webpack测试",
"sideEffects": [
"*.css",
+ "*.less",
+ "*.scss"
],
"main": "index.js",
"author": "wali",
"private": true,
"license": "MIT",
"scripts": {
"dev": "npx webpack-dev-server --colors --mode=development",
"prod": "npx webpack --colors --mode=production",
"build": "npx webpack --colors --mode=development",
"analyse": "npx webpack --profile --json> stats.json --colors --mode=development"
},
"dependencies": {
"@babel/core": "^7.4.5",
"@babel/plugin-syntax-dynamic-import": "^7.2.0",
"@babel/plugin-transform-runtime": "^7.4.4",
"@babel/polyfill": "^7.4.4",
"@babel/preset-env": "^7.4.5",
"@babel/runtime": "^7.4.5",
"@babel/runtime-corejs2": "^7.4.5",
"autoprefixer": "^9.5.1",
"babel-loader": "^8.0.6",
"clean-webpack-plugin": "^3.0.0",
"css-loader": "^2.1.1",
"extract-text-webpack-plugin": "^3.0.2",
"file-loader": "^3.0.1",
"html-loader": "^0.5.5",
"html-webpack-plugin": "^3.2.0",
"image-webpack-loader": "^4.6.0",
"json5-loader": "^2.0.0",
"less": "^3.9.0",
"less-loader": "^5.0.0",
"loadsh": "^0.0.4",
"lodash": "^4.17.11",
"mini-css-extract-plugin": "^0.7.0",
"node-sass": "^4.12.0",
"postcss-loader": "^3.0.0",
"sass-loader": "^7.1.0",
"style-loader": "^0.23.1",
"webpack": "^4.32.0",
"webpack-cli": "^3.3.2",
"webpack-dev-server": "^3.4.1"
},
"devDependencies": {
"webpack-bundle-analyzer": "^3.3.2"
}
}
index.js
import './assets/css/index.css';
assets/css/index.css
h1{
color: blue;
}
运行webpack
yarn run prod
ssl
打开dist/index.html,看到/assets/css/index.css文件样式生效了
ssl
<!--dist/index.html-->
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>title</title>
<link href="./assets/css/main.2df4cfd436df0ec42c4d.css" rel="stylesheet"></head>
<body>
<h1>欢迎来到瓦力博客</h1>
<span class="iconfont wali-icon-fuzhi"></span>
<img src="assets/images/wali_logo2BQg9e7.png" alt="">
<script type="text/javascript" src="./main.2df4cfd436df0ec42c4d.js"></script></body>
</html>
从index.html文件中可以看到css文件被提取出来，并且被引用。
3.提取sass
上面配置已经写了，在plugins.js和module.js文件中配置了，这里就简单的验证一下
修改index.js
import './assets/sass/index.scss';
assets/sass/index.scss
body{
h1{
transform: translate(100px, 100px);
}
}
运行webpack
yarn run prod
打开dist/index.html发现欢迎来到瓦力博客几个字发生偏移，说明/assets/sass/index.scss样式已经生效
ssl
4.提取less
上面配置已经写了，在plugins.js和module.js文件中配置了，这里就简单的验证一下
修改index.js
import './assets/less/index.less';
assets/less/index.less
body{
h1{
transform: rotate(90deg);
background: red;
text-align: center;
}
}
运行webpack
yarn run prod
打开dist/index.html发现欢迎来到瓦力博客几个字旋转90度，背景变红，字体居中，说明/assets/less/index.less样式已经生效
ssl
5.总结
测试这小节其实遇到几个问题，小菜写出来：
调试
这小节的测试命令都变成yarn run prod，是测试生产环境下webpack配置，生产环境下css,less,scss都会被压缩，去注释，index.html文件也会被压缩，去注释，还要添加域名。这样一来从生成的文件方面就不容易看出webpack到底是否配置正确。所以小菜将config.js中修改
+ publicPath: env == 'development'?'./':'./',
就是生成后index.html文件能直接在本地打开而不报错。
build/module.js修改
+ minimize:config.NODE_ENV === 'development'? false:false //是否压缩html
生成后index.html文件不要被压缩，还保留树形结构，便于查找
less和scss文件样式不起作用
小菜起初测试css文件，发现打包后css样式被提取出来，样式也生效了，但是换成
import './assets/less/index.less';
//或
import './assets/sass/index.scss';
时，在运行打包命令时，样式没有被提取出来。后来经过认真分析，发现/webpack/2019/05/24/webpack-10.html一节中配置了Tree Shaking。Tree shaking作用就是当我在index.js文件中使用import './assets/less/index.less'写法时，会检测在js文件中是否使用了引入来的less，很明显在index.js文件中没有使用，只是单纯的引入，所以Tree shaking就会自动帮我们过滤掉这行代码，就导致最终生成的js文件中没有样式，也就提取不出来样式了。
看了上面的解释，有的小伙伴可能会问import './assets/css/index.css'也在index.js文件中只引用没有使用，为什么css文件中的样式就能够生效呢？原因还是在/webpack/2019/05/24/webpack-10.html一节中，小菜在package.json中配置了css，没有配置less,scss。
"sideEffects": [
"*.css",
+ "*.less",
+ "*.scss"
],
当我们配置*.css,*.less,*.scss后，在Tree shaking时，webpack就会知道忽略css,less,scss所有文件，即使在js文件中css,less,scss只引用没有使用，也不要删除这行代码。
6.代码回滚
build/module.js
- minimize:config.NODE_ENV === 'development'? false:false //是否压缩html
+ minimize:config.NODE_ENV === 'development'? false:true //是否压缩html
build/base/config.js
let _mode = process.argv[process.argv.length - 1];
let env = _mode.replace(/--mode=(.+)/g,"$1");
let config = {
NODE_ENV: env == 'development'?'development':'production', //development 开发 production 线上
- publicPath: env == 'development'?'./':'./',
+ publicPath: env == 'development'?'./':'http://www.waliblog.com/',
apiUrl:'http://www.waliblog.com',
port: 9999
}
module.exports = config;
