create-react-app-purge-css

const path = require('path');
const fs = require('fs');
const glob = require('glob-all');

const appDirectory = fs.realpathSync(process.cwd());
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);

const PurgecssPlugin = require('purgecss-webpack-plugin');

module.exports = {
	webpack: {
		plugins: [
			new PurgecssPlugin({
				paths: [resolveApp('public/index.html'), ...glob.sync(`${resolveApp('src')}/**/**/*`, { nodir: true })],
			}),
		],
	},
};