Question

I just can’t get my head around how this is supposed to work: As I understand, a pretty common way to define a class/module in CoffeeScript is by using module.exports = class MyClass at the top of the file. I would also guess that the coffee compiler would facilitate this pattern. Take this minimalist example:

# src/Foo.coffee
module.exports = class Foo

# src/Bar.coffee
module.exports = class Bar

Then compile and join the two with:

coffee -cj all.js src

The result is all.js where module.exports is redefined/overwritten for each module:

// Generated by CoffeeScript 1.4.0
(function() {
  var Bar, Foo;

  module.exports = Bar = (function() {
    function Bar() {}
    return Bar;
  })();

  module.exports = Foo = (function() {
    function Foo() {}
    return Foo;
  })();

}).call(this);

If I now try to do this, the result would be an error stating that the Foo module cound not be found, and rightly so because the last module (here: Bar) has redefined module.exports to only contain itself.

Foo = require('foo');

I guess this is quite the noob question but I can’t seem to get a good answer anywhere.

Answer 1

This is pretty much the desired behaviour… You’re merging two modules into one, and they both want to be at the top level, so one of them has to win.

One possible solution would be as follows:

# src/Foo.coffee
module.exports.Foo = class Foo

# src/Bar.coffee
module.exports.Bar = class Bar

which yields:

# all.js
(function() {
  var Bar, Foo;

  module.exports.Bar = Bar = (function() {
    function Bar() {}
    return Bar;
  })();

  module.exports.Foo = Foo = (function() {
    function Foo() {}
    return Foo;
  })();

}).call(this);

And then you can use (in CoffeeScript)

{Foo, Bar} = require "all"

to get at the classes contained therein