Convert IPV6 to IPV4 if possible

By default uwebsockets.js returns the client's IP in ipv6 format This small piece of code will allow you to get IPV4 from IPV6

helper/ip.js

const parseIpv6 = (ip6str) => {
  const str = ip6str.toString();
  const ar = [];
  for (var i = 0; i < 8; i++) ar[i] = 0;
  if (str === '::') return ar;
  const sar = str.split(':');
  let slen = sar.length;
  if (slen > 8) slen = 8;
  let j = 0;
  i = 0
  for (i = 0; i < slen; i++) {
    if (i && sar[i] === '') {
      j = 9 - slen + i;
      continue;
    }
    ar[j] = parseInt(`0x0${sar[i]}`);
    j++;
  }
  return ar;
}

exports.convertIpv6toIpv4 = function(ip, force = false) {
  if (this.isValidIpv4(ip)){
    return ip;
  }
  if (force === true || /0000:0000:0000:0000:0000:/.test(ip)) {
    const ip6parsed = parseIpv6(ip);
    return `${ip6parsed[6] >> 8}.${ip6parsed[6] & 0xff}.${ip6parsed[7] >> 8}.${ip6parsed[7] & 0xff}`;
  }

  return ip;
}

exports.isValidIpv4 = function (ip) {
  let ipv4_pattern = /^(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)$/;
  if (!ipv4_pattern.test(ip)) {
    return false;
  }
  let token = ip.split('.');
  return (
    token[0] <= 255 && token[1] <= 255 && token[2] <= 255 && token[3] <= 255
  );
};

exports.isValidIpv6 = function (ip) {
  let ipv6_pattern = /^::|^::1|^([a-fA-F0-9]{1,4}::?){1,7}([a-fA-F0-9]{1,4})$/;
  return ipv6_pattern.test(ip);
};

exports.isValidIp = function (ip) {
  return this.isValidIpv4(ip) || this.isValidIpv6(ip);
};