Not sure why there isn't an "official" way of doing this (compared to what Ruby on Rails does).
Here are a few suggestions:
DIY
Here's what I've been doing so far:
At server startup, I run uglify-js on all the js files (under .../js, and create the minified version under .../min) with something like so (leaving out the reading/writing of the files):
var jsp = require('uglify-js').parser;
var pro = require('uglify-js').uglify;
var ast = jsp.parse(code.toString('utf8')); // parse code and get the initial AST
ast = pro.ast_mangle(ast); // get a new AST with mangled names
ast = pro.ast_squeeze(ast); // get an AST with compression optimizations
var final_code = pro.gen_code(ast); // compressed code here
then in html templates, based on some environment variable to trigger production environment, I generate the path for the <script>
tags to either point to .../js or .../min.
This leaves out quite a lot (where you would group all js files into one minimized one to reduce the number of browser queries and such), but hopefully this can help you craft your own strategy.
Piler
That said, I've been meaning to try piler (https://github.com/epeli/piler), which seems to be a better alternative to the DYI way.
Using Grunt
Grunt.js (http://gruntjs.com/) is also quite suitable to help preprocess files (html, js, css, ...)
Here are a few pointers: