# 五.webpack 自带优化

# 1.安装

package.json

{
  "name": "5.selfOptimize",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.4.0",
    "@babel/preset-env": "^7.4.2",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.5",
    "html-webpack-plugin": "^3.2.0",
    "webpack": "^4.29.6",
    "webpack-cli": "^3.3.0",
    "webpack-dev-server": "^3.2.1"
  },
  "dependencies": {
    "jquery": "^3.3.1",
    "moment": "^2.24.0"
  }
}

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# 2.文件

src/index.js

import calc from "./test"
//import 在生产环境下 会自动去掉没用的代码
//tree-shaking 把没用到的代码 自动删除掉
//es6 模块会把结果放到default上
//let calc= require('./test')

//scope hosting 作用域提升

let a = 1
let b = 2
let c = 3
let d = a + b + c //webpack中自动省略 可以简化代码
console.log(d)
console.log(calc.default.sum(1, 2))

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src/test.js

let sum = (a, b) => {
  return a + b + "sum"
}
let minus = (a, b) => {
  return a - b + "minus"
}
export default {
  sum,
  minus,
}

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# 3.配置

webpack.config.js

let path = require("path")
let HtmlWebpackPlugin = require("html-webpack-plugin")
let webpack = require("webpack")
module.exports = {
  mode: "production",
  entry: "./src/index.js",
  output: {
    filename: "bundle.js",
    path: path.resolve(__dirname, "dist"),
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "./public/index.html",
    }),
    new webpack.IgnorePlugin(/\.\/locale/, /moment/),
  ],
  module: {
    noParse: /jquery/, //不去解析jquery中的依赖库
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        include: path.resolve("src"),
        use: {
          loader: "babel-loader",
          options: {
            presets: ["@babel/preset-env", "@babel/preset-react"],
          },
        },
      },
    ],
  },
}

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# 4.打包

npx webpack

完整代码 (opens new window)

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