code: static boolean containsUnicodeEscape(String s) {
      String esc = REGEXP_ESCAPER.regexpEscape(s);
      for (int i = -1; (i = esc.indexOf("\\u", i + 1)) >= 0;) {
        int nSlashes = 0;
        while (i - nSlashes > 0 && '\\' == esc.charAt(i - nSlashes - 1)) {
          ++nSlashes;
        }
        // if there are an even number of slashes before the \ u then it is a
        // Unicode literal.
        if (0 == (nSlashes & 1)) { return true; }
      }
      return false;
    }
docs: true if the JavaScript string would contain a Unicode escape when written
  out as the body of a regular expression literal.