code: public String getJavascriptEngineName(String defaultJsEnginePropName) {
  
  		String jsEngineName = null;
  		if (StringUtils.isEmpty(defaultJsEnginePropName)) {
  			jsEngineName = getJavascriptEngineName();
  		} else {
  			jsEngineName = getProperty(defaultJsEnginePropName);
  			if (StringUtils.isEmpty(jsEngineName)) {
  				jsEngineName = getJavascriptEngineName();
  			}
  		}
  
  		return jsEngineName;
  	}
docs: Returns the name of JS engine to use
  
  @param defaultJsEnginePropName
  the default JS engine property name
  @return the name of JS engine to use