webpack合并js文件

在使用webpack进行项目打包时，可以使用webpack-merge插件来合并多个js文件，具体步骤如下：

1. 安装webpack-merge插件

npm install webpack-merge --save-dev

2. 创建不同的webpack配置文件，例如：

webpack.common.js：

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

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

webpack.prod.js：

const merge = require('webpack-merge');
const common = require('./webpack.common.js');

module.exports = merge(common, {
  mode: 'production'
});

webpack.dev.js：

const merge = require('webpack-merge');
const common = require('./webpack.common.js');

module.exports = merge(common, {
  mode: 'development',
  devtool: 'inline-source-map',
  devServer: {
    contentBase: './dist'
  }
});

3. 在package.json文件中添加打包命令

"scripts": {
  "dev": "webpack-dev-server --open --config webpack.dev.js",
  "build": "webpack --config webpack.prod.js"
}

4. 运行打包命令

npm run build

以上操作将会合并webpack.common.js和webpack.prod.js中的配置，并将最终打包结果输出到dist文件夹中的bundle.js文件中。