build script by pure nodejs

build.js

const browserify = require('browserify'),
      babelify   = require('babelify'),
      compressor = require('node-minify'),
      fs = require('fs');

process.env.NODE_ENV = 'production';

// for development enviroment
// "watch": "watchify -t babelify ./app/javascripts/components/message/app.js -o ./public/js/build.js -d",
// "build-css": "node-sass --include-path scss ./app/stylesheets/components/message/main.scss ./public/css/style.css",

const srcPath = './app/javascripts/components/',
      srcFile = 'app.js',
      dstPathOfJs = './public/js/';

const list = fs.readdirSync(srcPath);
list.forEach( (folder) => {
  if (folder.indexOf('.') !== 0) {

    let appName = folder;
    let genFile = 'bundle_' + appName + '.js',
        minFile = 'bundle_' + appName + '.min.js';

    Promise.resolve()
    .then(() => {
      return new Promise((resolve, reject) => {

        console.log('start to transpile -> ' + appName);

        browserify()
        .add(srcPath + folder + '/' + srcFile)
        .transform(babelify)
        .bundle((err,buf) => {
          console.log('transpile done! -> ' + appName);
          resolve(buf);
        });
      });
    })
    .then((buf) => {
      return new Promise((resolve, reject) => {

        console.log('start to write -> ' + genFile);

        let ws = fs.createWriteStream(dstPathOfJs + genFile);
        ws.write(buf, () => {
          console.log('write done! -> ' + genFile);
          resolve();
        });
      });
    })
    .then(() => {
      return new Promise((resolve, reject) => {

        console.log('start to compress -> ' + minFile);

        compressor.minify({
          compressor: 'uglifyjs',
          input: dstPathOfJs + genFile,
          output: dstPathOfJs + minFile,
          options: {
            warnings: true
          },
          callback: function(err, min) {
            console.log('compress done! -> ' + minFile);
            resolve();
          }
        });
      });
    })
    .then(() => {
      console.log('end ' + appName);
    })
    .catch((err) => {
      console.error(err);
      process.exit(1);
    });
  }
});