code: function isIdentifier(name, ecmaVersion) {
      if (ecmaVersion >= 6) {
          return esutils.keyword.isIdentifierES6(name);
      }
      return esutils.keyword.isIdentifierES5(name);
  }
docs: Determines if a string name is a valid identifier
  @param {string} name The string to be checked
  @param {int} ecmaVersion The ECMAScript version if specified in the parserOptions config
  @returns {boolean} True if the string is a valid identifier