Gulp.js - Automate and enhance your workflow
stealjs - Futuristic JavaScript dependency loader and builder. Speeds up application load times. Works with ES6, CommonJS, AMD, CSS, LESS and more. Simplifies modular workflows.
Grunt - The Grunt ecosystem is huge and it's growing every day.
RequireJS - RequireJS is a JavaScript file and module loader.
Webpack - Webpack is a module bundler. Its main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset.
JSPM - Front End Package Manager, Frontend Development, and Javascript