Effortlessly extend class methods in CoffeeScript

decorate.coffee

decorate = (klass, methodName, fn) ->
  method = klass::[methodName]
  klass::[methodName] = (args...) ->
    method.apply this, args
    fn.apply this, args


# Example

decorate Array, 'push', (args...) ->
  console.log "pushing #{args.length} items: #{args.join(', ')}"

array = []
array.push 'foo', 'bar', 'baz' # => pushing 3 items: foo, bar, baz