Why doing this we can use ES6 modular and use browserify or webpack to bundle the generated scripts…
Bashar Ayyash

I guess Gulp is only one of the possible ways. Such automation tools are widely used with popular libraries like jQuery (through Grunt), underscore.js, and even AngularJS itself. The point is that usually front-end developers are using Gulp or any other for CSS auto-prefixing, minification and concatenation; so it can be easily extended with required JS code processing steps.