webpack.config.js

const path = require('path');

module.exports = env=>{

    let devConfig = {};
    if(env.NODE_ENV==='development'){
        devConfig = {...{
                devtool:'inline-source-map',
                devServer: {
                    index:'index.html',
                    contentBase: './example'
                },
            }};
    }

    return {
        mode:env.NODE_ENV,
        entry: {"ua-trace":'./src/index.js'},
        ...devConfig,
        module: {
            rules: [
                {
                    test: /\.js$/,
                    exclude: /node_modules/,
                    use:[
                        {
                            loader: 'babel-loader',
                            options: {
                                presets: ['@babel/preset-env']
                            }
                        },
                        {
                            loader: "eslint-loader",
                            options: {
                                // eslint options (if necessary)
                                fix:true,
                                configFile:'./.eslintrc.json'
                            }
                        }

                    ]

                },
            ],
        },
        output: {
            path: path.resolve(__dirname, 'dist'),
            filename: '[name].js',
            library:'UATrace',
            libraryTarget:'umd'
        },
    }
}