code: function jsEscape(s) {
    var result = '"';
    for (var i = 0; i < s.length; i++) {
      let cp = s.charCodeAt(i);
      let special = specialEscape[cp];
      if (special !== undefined) {
        result += special;
      } else if (cp >= 0x20 && cp <= 0x7e) {
        result += String.fromCodePoint(cp);
      } else {
        result += '\\u' + zeroPaddedHex(cp, 4);
      }
    }
    result += '"';
    return result;
  }
docs: Returns a double-quoted Java or JavaScript string with all
  non-printable and non-US-ASCII sequences escaped.
  
  @param {string} str Valid Unicode string
  @return {string}    Double-quoted string with Unicode sequences escaped