rubylikeincludes.coffee

Function::include = (otherClass) ->
  for name, method of otherClass::
    this::[name] = method
  return

class Bar
  b: -> console.log 'b'

class Foo
  @include Bar
  a: -> console.log 'a'

x = new Foo()
x.a()
x.b()

rubylikeincludes.js

var Bar, Foo, x;

Function.prototype.include = function(otherClass) {
  var method, name, _ref;
  _ref = otherClass.prototype;
  for (name in _ref) {
    method = _ref[name];
    this.prototype[name] = method;
  }
};

Bar = (function() {
  function Bar() {}
  Bar.prototype.b = function() {
    return console.log('b');
  };
  return Bar;
})();

Foo = (function() {
  function Foo() {}
  Foo.include(Bar);
  Foo.prototype.a = function() {
    return console.log('a');
  };
  return Foo;
})();

x = new Foo();
x.a();
x.b();