珠峰架构师成长计划

1. webpack介绍 #

webpack是一个JavaScript 应用程序的静态模块打包工具

webpack

1.1 安装 #

npm install  webpack webpack-cli --save-dev

1.2 入口(entry) #

入口起点(entry point)指示 webpack 应该使用哪个模块，来作为构建其内部依赖图(dependency graph) 的开始。进入入口起点后，webpack 会找出有哪些模块和库是入口起点（直接和间接）依赖的
默认值是 ./src/index.js，但你可以通过在 webpack configuration 中配置 entry 属性，来指定一个（或多个）不同的入口起点

1.2.1 src\index.js #

import './index.css'

1.2.2 index.css #

body{
  background-color:green;
}

1.2.3 webpack.config.js #

const path = require('path');
module.exports = {
  entry: './src/index.js',
};

1.3 输出(output) #

output 属性告诉 webpack 在哪里输出它所创建的 bundle，以及如何命名这些文件
主要输出文件的默认值是 ./dist/main.js，其他生成文件默认放置在 ./dist 文件夹中。

webpack.config.js

const path = require('path');
module.exports = {
  entry: './src/index.js',
+  output: {
+    path: path.resolve(__dirname, 'dist'),
+    filename: 'main.js'
+  }
};

1.4 loader #

webpack 只能理解 JavaScript 和 JSON 文件
loader 让 webpack 能够去处理其他类型的文件，并将它们转换为有效模块，以供应用程序使用，以及被添加到依赖图中

webpack.config.js

const path = require('path');
module.exports = {
  mode: 'development',
  devtool:false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'main.js'
  },
+  module: {
+    rules: [
+      { test: /\.css$/, use: ['style-loader','css-loader']}
+    ]
+  }
};

1.5 插件(plugin) #

loader 用于转换某些类型的模块，而插件则可以用于执行范围更广的任务。包括：打包优化，资源管理，注入环境变量

1.5.1 src\index.html #

src\index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>webpack5</title>
</head>
<body>
</body>
</html>

1.5.2 webpack.config.js #

const path = require('path');
+const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
  mode: 'development',
  devtool:false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'main.js'
  },
  module: {
    rules: [
      { test: /\.css$/, use: ['style-loader','css-loader']}
    ]
  },
+  plugins: [
+    new HtmlWebpackPlugin({template: './src/index.html'})
+  ]
};

1.6 模式(mode) #

webpack 4.x 版本引入了 mode 的概念

1.6.1 环境差异 #

开发环境
- 需要生成 sourcemap 文件
- 需要打印 debug 信息
- 需要 live reload 或者 hot reload 的功能
生产环境
- 可能需要分离 CSS 成单独的文件，以便多个页面共享同一个 CSS 文件
- 需要压缩 HTML/CSS/JS 代码
- 需要压缩图片
其默认值为 production

1.6.2 区分环境 #

--mode用来设置模块内的process.env.NODE_ENV
cross-env用来设置node环境的process.env.NODE_ENV
DefinePlugin用来设置模块内的全局变量

1.6.2.1 命令行配置 #

webpack的mode默认为production
webpack serve的mode默认为development
可以在模块内通过process.env.NODE_ENV获取当前的环境变量,无法在webpack配置文件中获取此变量

  "scripts": {
    "build": "webpack",
    "dev": "webpack serve"
  },

index.js

console.log(process.env.NODE_ENV);// development | production

webpack.config.js

console.log('NODE_ENV',process.env.NODE_ENV);// undefined

1.6.2.2 命令行配置 #

  "scripts": {
    "build": "webpack --mode=production",
    "dev": "webpack --mode=development serve"
  },

1.6.2.3 mode配置 #

module.exports = {
  mode: 'development'
}

1.6.2.4 DefinePlugin #

可以在任意模块内通过 process.env.NODE_ENV 获取当前的环境变量
但无法在node环境(webpack 配置文件中)下获取当前的环境变量

plugins:[
   new webpack.DefinePlugin({
      'process.env.NODE_ENV':JSON.stringify(process.env.NODE_ENV)
   })
]

index.js

console.log(NODE_ENV);//  production

webpack.config.js

console.log('process.env.NODE_ENV',process.env.NODE_ENV);// undefined
console.log('NODE_ENV',NODE_ENV);// error ！！！

1.6.2.5 cross-env #

只能设置node环境下的变量NODE_ENV

package.json

"scripts": {
  "build": "cross-env NODE_ENV=development webpack"
}

webpack.config.js

console.log('process.env.NODE_ENV',process.env.NODE_ENV);// development

2 开发服务器 #

2.1 安装服务器 #

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

2.2 webpack.config.js #

类别	配置名称	描述
output	path	指定输出到硬盘上的目录
output	publicPath	表示的是打包生成的index.html文件里面引用资源的前缀
devServer	publicPath	表示的是打包生成的静态文件所在的位置(若是devServer里面的publicPath没有设置，则会认为是output里面设置的publicPath的值)
devServer	static	用于配置提供额外静态文件内容的目录

2.3 webpack.config.js #

module.exports = {
  devServer: {
    static: path.resolve(__dirname, 'public'),
    port: 8080,
    open: true
  }
}

2.4 package.json #

  "scripts": {
    "build": "webpack",
+   "dev": "webpack serve"
  }

3. 支持CSS #

css-loader用来翻译处理@import和url()
style-loader可以把CSS插入DOM中

3.1 安装模块 #

npm i style-loader css-loader -D

3.2 webpack.config.js #

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
  mode: 'development',
  devtool:false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js'
  },
  module: {
    rules: [
     { test: /\.css$/, use: ['style-loader','css-loader'] }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({template: './src/index.html'})
  ]
};

3.3 src\bg.css #

src\bg.css

body{
    background-color: green;
}

3.4 src\index.css #

src\index.css

@import "./bg.css";
body{
    color:red;
}

3.5 src\index.js #

src\index.js

+import './index.css';

4. 支持less和sass #

node-sass

4.1 安装 #

npm i less less-loader -D
npm i node-sass sass-loader -D
npm rebuild node-sass

4.2 webpack.config.js #

webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
  mode: 'development',
  devtool: false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js'
  },
  module: {
    rules: [
      { test: /\.css$/, use: ['style-loader', 'css-loader'] },
+     { test: /\.less$/, use: ['style-loader','css-loader', 'less-loader'] },
+     { test: /\.scss$/, use: ['style-loader','css-loader', 'sass-loader'] }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({ template: './src/index.html' })
  ]
};

4.3 src\index.html #

src\index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>webpack5</title>
</head>
<body>
+  <div id="less-container">less-container</div>
+  <div id="sass-container">sass-container</div>
</body>
</html>

4.4 src\index.js #

src\index.js

import './index.css';
+import './less.less';
+import './sass.scss';

4.5 src\less.less #

src\less.less

@color:blue;
#less-container{
    color:@color;
}

4.6 src\sass.scss #

src\sass.scss

$color:orange;
#sass-container{
    color:$color;
}

5. CSS兼容性 #

为了浏览器的兼容性，有时候我们必须加入-webkit,-ms,-o,-moz这些前缀
- Trident内核：主要代表为IE浏览器, 前缀为-ms
- Gecko内核：主要代表为Firefox, 前缀为-moz
- Presto内核：主要代表为Opera, 前缀为-o
- Webkit内核：产要代表为Chrome和Safari, 前缀为-webkit
伪元素::placeholder可以选择一个表单元素的占位文本，它允许开发者和设计师自定义占位文本的样式。

5.1 安装 #

https://caniuse.com/
postcss-loader可以使用PostCSS处理CSS
postcss-preset-env把现代的CSS转换成大多数浏览器能理解的
PostCSS Preset Env已经包含了autoprefixer和browsers选项

npm i postcss-loader postcss-preset-env -D

5.2 postcss.config.js #

postcss.config.js

let postcssPresetEnv = require('postcss-preset-env');
module.exports={
    plugins:[postcssPresetEnv({
        browsers: 'last 5 version'
    })]
}

5.3 webpack.config.js #

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
  mode: 'development',
  devtool: false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js'
  },
  module: {
    rules: [
+     { test: /\.css$/, use: ['style-loader', 'css-loader','postcss-loader'] },
+     { test: /\.less$/, use: ['style-loader','css-loader','postcss-loader','less-loader'] },
+     { test: /\.scss$/, use: ['style-loader','css-loader','postcss-loader','sass-loader'] }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({ template: './src/index.html' })
  ]
};

5.4 src\index.css #

src\index.css

@import "./bg.css";
body{
    color:red;
}
+#root {
+    background-color: red;
+    width: 100px;
+    height: 10px;
+    transform: rotate(10deg);
+}

5.5 src\index.html #

src\index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>webpack5</title>
</head>
<body>
  <div id="less-container">less-container</div>
  <div id="sass-container">sass-container</div>
+ <div id="root"></div>
</body>
</html>

5.6 package.json #

{
+  "browserslist": {
+    "development": [
+      "last 1 chrome version",
+      "last 1 firefox version",
+      "last 1 safari version"
+    ],
+    "production": [
+      ">0.2%"
+    ]
+  }
}

6 资源模块 #

资源模块是一种模块类型，它允许使用资源文件（字体，图标等）而无需配置额外 loader
raw-loader => asset/source 导出资源的源代码
file-loader => asset/resource 发送一个单独的文件并导出 URL
url-loader => asset/inline 导出一个资源的 data URI
asset 在导出一个 data URI 和发送一个单独的文件之间自动选择。之前通过使用 url-loader，并且配置资源体积限制实现
Rule.type
asset-modules

6.1 webpack.config.js #

module.exports = {
    module:{
        rules: [
            {
                test: /\.js$/,
                use: [
                    {
                        loader: 'babel-loader',
                        options: {
                            presets: [
                                "@babel/preset-react"
                            ]
                        },

                    }
                ],
                exclude:/node_modules/
            },
+           {
+               test: /\.png$/,
+               type: 'asset/resource'
+           },
+           {
+               test: /\.ico$/,
+               type: 'asset/inline'
+           },
+           {
+               test: /\.txt$/,
+               type: 'asset/source'
+           },
+           {
+               test: /\.jpg$/,
+               type: 'asset',
+               parser: {
+                   dataUrlCondition: {
+                     maxSize: 4 * 1024 // 4kb
+                   }
+               }
+           }
        ]
    },
  experiments: {
    asset: true
  },
};

6.2 src\index.js #

src\index.js

+ import png from './assets/logo.png';
+ import ico from './assets/logo.ico';
+ import jpg from './assets/logo.jpg';
+ import txt from './assets/logo.txt';
+ console.log(png,ico,jpg,txt);

7 JS兼容性处理 #

Babel其实是一个编译JavaScript的平台,可以把ES6/ES7,React的JSX转义为ES5

7.1 @babel/preset-env #

Babel默认只转换新的最新ES语法,比如箭头函数

7.1.1 安装依赖 #

babel-loader使用Babel和webpack转译JavaScript文件
@babel/@babel/coreBabel编译的核心包
babel-preset-env
@babel/@babel/preset-reactReact插件的Babel预设
@babel/plugin-proposal-decorators把类和对象装饰器编译成ES5
@babel/plugin-proposal-class-properties转换静态类属性以及使用属性初始值化语法声明的属性

npm i babel-loader @babel/core @babel/preset-env @babel/preset-react  -D
npm i @babel/plugin-proposal-decorators @babel/plugin-proposal-class-properties @babel/plugin-proposal-private-property-in-object  @babel/plugin-proposal-private-methods -D

7.1.2 webpack.config.js #

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
  mode: 'development',
  devtool: false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'main.js',
  },
  module: {
    rules: [
+      {
+        test: /\.jsx?$/,
+        use: {
+          loader: 'babel-loader',
+          options: {
+            presets: ["@babel/preset-env", '@babel/preset-react'],
+            plugins: [
+              ["@babel/plugin-proposal-decorators", { legacy: true }],
+              ["@babel/plugin-proposal-private-property-in-object", { "loose": true }],
+              ["@babel/plugin-proposal-private-methods", { "loose": true }],
+              ["@babel/plugin-proposal-class-properties", { loose: true }],
+            ],
+          },
+        },
+      },
      { test: /\.css$/, use: ['style-loader', 'css-loader', 'postcss-loader'] },
      { test: /\.less$/, use: ['style-loader', 'css-loader','postcss-loader', 'less-loader'] },
      { test: /\.scss$/, use: ['style-loader', 'css-loader', 'postcss-loader','sass-loader'] },
      {
        test: /\.(jpg|png|gif|bmp|svg)$/,
        type:'asset/resource',
        generator:{
          filename:'images/[hash][ext]'
        }
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({ template: './src/index.html' })
  ]
};

7.1.3 src\index.js #

src\index.js

+function readonly(target,key,descriptor) {
+    descriptor.writable=false;
+}
+
+class Person{
+    @readonly PI=3.14;
+}
+let p1=new Person();
+p1.PI=3.15;
+console.log(p1)

7.1.4 jsconfig.json #

jsconfig

jsconfig.json

{
    "compilerOptions": {
        "experimentalDecorators": true
    }
}

8. ESLint代码校验 #

8.1 安装 #

npm install eslint eslint-loader babel-eslint --D

8.2 webpack.config.js #

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
  mode: 'development',
  devtool: false,
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js',
  },
  module: {
    rules: [
+      {
+        test: /\.jsx?$/,
+        loader: 'eslint-loader',
+        enforce: 'pre',
+        options: { fix: true },
+        exclude: /node_modules/,
+      },
      {
        test: /\.jsx?$/,
        use: {
          loader: 'babel-loader',
          options: {
            "presets": ["@babel/preset-env"],
            "plugins": [
              ["@babel/plugin-proposal-decorators", { legacy: true }],
              ["@babel/plugin-proposal-private-property-in-object", { "loose": true }],
              ["@babel/plugin-proposal-private-methods", { "loose": true }],
              ["@babel/plugin-proposal-class-properties", { loose: true }],
            ]
          }
        },
        include: path.join(__dirname, 'src'),
        exclude: /node_modules/
      },
      { test: /\.css$/, use: ['style-loader', 'css-loader', 'postcss-loader'] },
      { test: /\.less$/, use: ['style-loader', 'css-loader','postcss-loader', 'less-loader'] },
      { test: /\.scss$/, use: ['style-loader', 'css-loader', 'postcss-loader','sass-loader'] },
      {
        test: /\.(jpg|png|bmp|gif|svg)$/, use: [{
          loader: 'url-loader', options: {
            limit: 10
          }
        }]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({ template: './src/index.html' })
  ]
};

8.3 src\index.html #

src\index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>webpack5</title>
</head>
<body>
+  <div id="root"></div>
</body>
</html>

8.4 src\index.js #

src\index.js

+import React from "react";
+import ReactDOM from "react-dom";
+ReactDOM.render("hello",document.getElementById("root"));
+
+function readonly(target,key,descriptor) {
+    descriptor.writable=false;
+}
+
+class Person{
+    @readonly PI=3.14;
+}
+let p1=new Person();
+p1.PI=3.15;

8.5 .eslintrc.js #

.eslintrc.js

module.exports = {
    root: true,
    parser:"babel-eslint",
    //指定解析器选项
    parserOptions: {
        sourceType: "module",
        ecmaVersion: 2015
    },
    //指定脚本的运行环境
    env: {
        browser: true,
    },
    // 启用的规则及其各自的错误级别
    rules: {
        "indent": "off",//缩进风格
        "quotes":  "off",//引号类型 
        "no-console": "error",//禁止使用console
    }
}

8.6 airbnb #

eslint-config-airbnb

npm i eslint-config-airbnb eslint-loader eslint eslint-plugin-import eslint-plugin-react eslint-plugin-react-hooks and eslint-plugin-jsx-a11y -D

eslintrc.js

module.exports = {
    "parser":"babel-eslint",
    "extends":"airbnb",
    "rules":{
        "semi":"error",
        "no-console":"off",
        "linebreak-style":"off",
        "eol-last":"off"
        //"indent":["error",2]
    },
    "env":{
        "browser":true,
        "node":true
    }
}

8.7 自动修复 #

安装vscode的eslint插件
配置自动修复参数

.vscode\settings.json

{
    "eslint.validate": [
        "javascript",
        "javascriptreact",
        "typescript",
        "typescriptreact"
    ],
    "editor.codeActionsOnSave": {
        "source.fixAll.eslint": true
    }
  }

9. 服务器代理 #

如果你有单独的后端开发服务器 API，并且希望在同域名下发送 API 请求，那么代理某些 URL 会很有用。

9.1 不修改路径 #

请求到 /api/users 现在会被代理到请求 http://localhost:3000/api/users。

devServer: {
  proxy: {
    "/api": 'http://localhost:3000'
  }
}

9.2 修改路径 #

devServer: {
  proxy: {
      "/api": {
       target: 'http://localhost:3000',
       pathRewrite:{"^/api":""}        
      }            
  }
}

9.3 onBeforeSetupMiddleware #

onBeforeSetupMiddleware 在 webpack-dev-server 静态资源中间件处理之前，可以用于拦截部分请求返回特定内容，或者实现简单的数据 mock。

devServer: {
onBeforeSetupMiddleware(devServer){// express()
    devServer.app.get('/api/users', (req, res) => {
      res.json([{ id: 1 }, { id: 2 }]);
    });
}
}

9.4 webpack-dev-middleware #

webpack-dev-middleware就是在 Express 中提供 webpack-dev-server 静态服务能力的一个中间件

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

const express = require('express');
const app = express();
const webpack = require('webpack');
const webpackDevMiddleware = require('webpack-dev-middleware');
const webpackOptions = require('./webpack.config');
webpackOptions.mode = 'development';
const compiler = webpack(webpackOptions);
app.use(webpackDevMiddleware(compiler, {}));
app.listen(3000);

webpack-dev-server 的好处是相对简单，直接安装依赖后执行命令即可
而使用webpack-dev-middleware的好处是可以在既有的 Express 代码基础上快速添加 webpack-dev-server 的功能，同时利用 Express 来根据需要添加更多的功能，如 mock 服务、代理 API 请求等