Webpack has quickly become one of the most popular choices among web developer build tools.  It can quickly build, minify, split & do a whole wonder of other things to your code.
Sample Webpack Config: 
https://gist.github.com/learncodeacademy/25092d8f1daf5e4a6fd3Node.js Introduction: 
https://www.youtube.com/watch?v=pU9Q6oiQNd0In this webpack tutorial, I'm going to cover a very basic configuration for webpack that will get you started in a project.  It will build all of your Javascript and minify and dedupe the code for production.  To code react, we just have a little more configuration to add to our webpack config.  That will have a full HTML, CSS, JS react application going.
Another great build tool is Browserify, which at the beginning of the process works a LOT like Webpack, but in the end, Webpack is a lot more featureful.