# 三.watch 的用法

# 1.安装

package.json

{
  "name": "3.watch",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "webpack-dev-server"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "html-webpack-plugin": "^3.2.0",
    "webpack": "^4.29.6",
    "webpack-cli": "^3.3.0",
    "webpack-dev-server": "^3.2.1"
  }
}

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# 2.文件

# 1.src/index.js

console.log("index")

# 2.index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>webpack配置watch</title>
  </head>

  <body></body>
</html>

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# 3.配置

webpack.config.js

const path = require("path")
let HtmlWebpackPlugin = require("html-webpack-plugin")

module.exports = {
  mode: "production",
  entry: {
    home: "./src/index.js",
  },
  output: {
    filename: "[name].js",
    path: path.resolve(__dirname, "dist"),
  },
  watch: true,
  //监控选项
  watchOptions: {
    poll: 1000, //每秒 问我 1000次
    aggregateTimeout: 500, //防抖 我一直输入代码
    ignored: /node_modules/, //忽略监控的文件夹
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html",
      filename: "index.html",
    }),
  ],
}

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# 4.运行

npm run dev

修改 js 文件，查看控制台发现页面会自动刷新

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