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12.webpack闯关.md

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webpack 大闯关

目标一：用webpack 转译 JS

  1. 去

    官网看初始化教程

  2. 创建文件并运行以下代码

    npm init -y

  3. 本地安装webpack 和 webpack-cli

    yarn add webpack@4 webpack-cli@3 --dev

  4. 新建src文件夹 并新建index.js文件

    console.log('hi')

  5. npx webpack本地运行 webpack

  6. 你会发现生成了一个main.js

    !function(e){var t={};function n(r){if(t[r])return t[r].exports;var o=t[r]={i:r,l:!1,exports:{}};return e[r].call(o.exports,o,o.exports,n),o.l=!0,o.exports}n.m=e,n.c=t,n.d=function(e,t,r){n.o(e,t)||Object.defineProperty(e,t,{enumerable:!0,get:r})},n.r=function(e){"undefined"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(e,Symbol.toStringTag,{value:"Module"}),Object.defineProperty(e,"__esModule",{value:!0})},n.t=function(e,t){if(1&t&&(e=n(e)),8&t)return e;if(4&t&&"object"==typeof e&&e&&e.__esModule)return e;var r=Object.create(null);if(n.r(r),Object.defineProperty(r,"default",{enumerable:!0,value:e}),2&t&&"string"!=typeof e)for(var o in e)n.d(r,o,function(t){return e[t]}.bind(null,o));return r},n.n=function(e){var t=e&&e.__esModule?function(){return e.default}:function(){return e};return n.d(t,"a",t),t},n.o=function(e,t){return Object.prototype.hasOwnProperty.call(e,t)},n.p="",n(n.s=0)}([function(e,t){console.log("hi")}]);

  7. 新建文件x.js

    export default 'xxx'

  8. 在index.js中导入

    import x from './x.js'
console.log(x)

  9. 再次运行npx webpack

    ...console.log("xxx")}]);

    会看到x.js被成功解析出来

  10. 干掉 warning 提示

新建 webpack.config.js

module.exports = {
  mode: 'development',

};

  1. webpack 配置 entry 和 output

    const path = require('path');

module.exports = {
  mode: 'development',
  entry: './src/index.js',
  output: {
    filename: 'index.js',
  },
};

目标二：理解文件名中的 hash 的用途

const path = require('path');

module.exports = {
  mode: 'development',
  entry: './src/index.js',
  output: {
    // filename: 'index.js',
    filename: '[name].[contenthash]'
  },
};

目标三：用 webpack 解析 HTML

html-webpack-plugin

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

module.exports = {
  entry: 'index.js',
  output: {
    path: path.resolve(__dirname, './dist'),
    filename: 'index_bundle.js',
  },
  plugins: [new HtmlWebpackPlugin()],
};

webpack.config.js删除多余的代码

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

module.exports = {
  mode: 'development',
  entry: './src/index.js',
  output: {
    filename: 'index.[contenthash].js'
  },
  plugins: [new HtmlWebpackPlugin({
    title: '我的 webpack demo',
    template: 'src/assets/index.html'
  })],
};

src/assets/index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>><%= htmlWebpackPlugin.options.title %></title>
</head>
<body>
<div id="#app"></div>
</body>
</html>

目标四：用 webpack 引入 CSS

(css-loader)[https://webpack.js.org/loaders/css-loader/]

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: ["style-loader", "css-loader"],
      },
    ],
  },
};

``webpack.config.js`

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

module.exports = {
  mode: 'development',
  entry: './src/index.js',
  output: {
    filename: 'index.[contenthash].js'
  },
  plugins: [new HtmlWebpackPlugin({
    title: '我的 webpack demo',
    template: 'src/assets/index.html'
  })],
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: ['style-loader', 'css-loader'],
      },
    ],
  },
};

单独引入css文件

(css-extract)[https://v4.webpack.js.org/plugins/mini-css-extract-plugin/]

webpack.config.js

const MiniCssExtractPlugin = require("mini-css-extract-plugin");

module.exports = {
  plugins: [new MiniCssExtractPlugin()],
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [MiniCssExtractPlugin.loader, "css-loader"],
      },
    ],
  },
};

根据环境不同 用不同的css加载方式

 "scripts": {
    "start": "webpack-dev-server --open",
    "build": "rm -rf dist && webpack --config webpack.config.prod.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },

题外话：使用 webpack div server

(wabpack-dev-server)[https://github.com/webpack/webpack-dev-server]

webpack div server 会在内存中完成这一切，而不输出dist目录

webpack.config.js

devtool: 'inline-source-map',
  devServer: {
    after: function (app, server, compiler) {
      // do fancy stuff
    }
  },

package.json

"scripts": {
+  "start": "webpack-dev-server --open",
  "build": "rm -rf && webpack",
  "test": "echo \"Error: no test specified\" && exit 1"
},

webpack 如何解决开发时的跨域问题？

在开发时，我们的页面在 localhost:8080，JS 直接访问后端接口（如 https://xiedaimala.com 或 http://localhost:3000）会报跨域错误。

为了解决这个问题，可以在 webpack.config.js 中添加如下配置：

module.exports = {
  //...
  devServer: {
    proxy: {
      '/api': {
        target: 'http://xiedaimala.com',
        changeOrigin: true,
      },
    },
  },
};