gistfile1.rb

class JavascriptObfuscator
  def self.obfuscate(source)
    new(source).obfuscate
  end
  
  def initialize(source)
    @source = source
    @last_identifier = "a"
    @translations = { }
  end
  
  def obfuscate
    @source.gsub(/((?:\{|,|\.)\s*)_(\w+)/m) do
      $1 + "_" + translation_for_identifier($2)
    end
  end
  
  private
    def translation_for_identifier(identifier)
      @translations[identifier] ||= next_identifier
    end
    
    def next_identifier
      returning(@last_identifier) do
        @last_identifier = @last_identifier.succ
      end
    end
end

if __FILE__ == $0
  print JavascriptObfuscator.obfuscate(File.read(ARGV[0]))
end