whole_func_string: function getExt(filename){
      var splitted = filename.split('.');
      if(splitted.length === 1) return ''; // file has no extension
      return splitted[splitted.length - 1]; // get file extension
  }
func_code_string: function getExt(filename){
      var splitted = filename.split('.');
      if(splitted.length === 1) return ''; // file has no extension
      return splitted[splitted.length - 1]; // get file extension
  }
func_documentation_string: helper - extract file extension from file name
  @param {String} filename
  @returns {String}  file extension