def js_compressor # :nodoc:
      case config.js_compressor
      when Crush::Engine
        config.js_compressor
      when Symbol, String
        JS_COMPRESSORS[config.js_compressor.to_sym]
      else
        Crush.register_js
        Tilt['js']
      end
    end
def js_compressor # :nodoc:
      case config.js_compressor
      when Crush::Engine
        config.js_compressor
      when Symbol, String
        JS_COMPRESSORS[config.js_compressor.to_sym]
      else
        Crush.register_js
        Tilt['js']
      end
    end
Returns the Javascript compression engine, based on
 what's set in `config.js_compressor`. If `config.js_compressor`
 is nil, let Tilt + Crush decide which one to use.