JS style event emitter in Ruby

EventEmitter.rb

class EventEmitter

  def initialize()
    @callbacks = {}
  end
  
  def on(event, &callback)
    @callbacks[event] ||= []
    @callbacks[event].push(callback)
  end

  def off(event)
    @callbacks[event] = nil;
  end

  def emit(event, *args)
    if @callbacks[event]
      @callbacks[event].each do |callback|
        callback.call args
      end
    end
  end

end

usage.rb

require './EventEmitter'

ev = EventEmitter.new

ev.on('hello') { |*args|
  args.each { |arg|
    puts arg
  }
}

ev.emit('hello', 'world', 'it\'s', 'december', 'almost', 'christmas', 'time', 'for', 'presents')