watch, browserify, babelify, uglify
npm install IFY-gulp-kitall js files in src will be automatically compiled down and minified as you make changes (to dist folder). Files will keep same names and uglified versions will have a .min.js suffix.
I personally use this to convert my es6 and es7 code to es5 supported by older browsers as well as require/import other js files. In v2.0.0 I added support for .sass files.
src/main.js (babel) => dist/main.js + dist/main.min.js
src/styles.sass => dist/styles.css + dist/styles.min.css