webpack.config.js

var path = require('path');

module.exports = {
    entry: './src/main/webapp/src/index.js',
    devtool: 'sourcemaps',
    cache: true,
    mode: 'development',
    output: {
        path: __dirname,
        filename: './src/main/resources/static/built/bundle.js'
    },
    module: {
        rules: [
            {
                test: path.join(__dirname, '.'),
                exclude: /(node_modules)/,
                use: [{
                    loader: 'babel-loader',
                    options: {
                        presets: ["@babel/preset-env", "@babel/preset-react", {'plugins': ['@babel/plugin-proposal-class-properties']}]
                    }
                }]
            },
            {
                test: /\.css$/,
                exclude: /node_modules/,
                loaders: [
                    'style-loader',
                    'css-loader'
                ],
            },
            {
                test: /\.css$/,
                loaders: ['style-loader', 'css-loader'],
                include: [
                    path.resolve(__dirname, './node_modules/codemirror/lib/'),
                    path.resolve(__dirname, './node_modules/codemirror/theme/')
                ]
            }
        ]
    }
};