gistfile1.coffee

mixins = {}
registerMixin = (name, mixin) -> mixins[name] = mixin

defaultMixins = ['event-janitor']

registerMixin 'event-janitor', EventJanitor
registerMixin 'remember-me', RememberMe

MixMaster = (mixins...) ->
  out = _.clone defaultMixins
  for mixin in mixins
    if mixin[0] is '+'
      out = _.union out, mixin.substring(1)
    else
      out = _.without out, mixin.substring(1)
      
  Mixen out
  
# You can now make classes like this:
class MyView extends MixMaster('+remember-me', '-event-janitor')