code: function isIdentifierStart(ch) {
          return (ch === '$') || (ch === '_') || (ch === '\\') ||
              (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') ||
              ((ch.charCodeAt(0) >= 0x80) && Regex.NonAsciiIdentifierStart.test(ch));
      }
docs: 7.6 Identifier Names and Identifiers