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mapcat is a simple utility that concatenates JavaScript files while also consolidating the corresponding source map files. It is useful if you use compile-to-JS languages whose compiler emits source map files. This is the case for CoffeeScript "transpiler" version 1.6 or later.

It's very easy to use:

bin/mapcat -m -j output.js

You specify the input by specifying the associated source map files - mapcat will find the actual JavaScript source files. Use -m to specify one output source map file and -j to specify one output JavaScript file. Invoke without any argument to see the (short) full help.


There is a simple example project in the example folder. Run bash to build the project. Then open index.html with Webkit Nightly or Chrome with Source Map support turned on in the Developer Tools. If you have Scripts panel enabled, refresh the page and you will see the program pause at a predefined debugger line, and you are looking at, CoffeeScript!

WebKit Source Map support shows in developer tools


You can also use the simple API. It exposes one simple function:

var cat = require('mapcat').cat;
cat(['', ''], 'output.js', '');