tmp

  // regex to check that each octet is valid
    var er = /^[0-9]+$/;
    // ipv4 octets are delimited by dot
    octets = val.split('.');
    // check 1: ipv4 address should contains 4 octets
    if (octets.length != 4)
      return false;

    for (let i = 0; i < octets.length; i++) {
      const element = octets[i];
      // check 2: each octet should be integer bigger than 0
      if (!er.test(element))
        return false;

      // check 3: each octet value should be less than 256
      var octetValue = parseInt(element);
      if (octetValue >= 256)
        return false;
    }

    // if all checks passed, we know it's valid IPv4 address!
    return true;