code: function DetectLocalIPAddress(callback) {
              if (!DetectRTC.isWebRTCSupported) {
                  return;
              }
  
              if (DetectRTC.isORTCSupported) {
                  return;
              }
  
              getIPs(function(ip) {
                  //local IPs
                  if (ip.match(/^(192\.168\.|169\.254\.|10\.|172\.(1[6-9]|2\d|3[01]))/)) {
                      callback('Local: ' + ip);
                  }
  
                  //assume the rest are public IPs
                  else {
                      callback('Public: ' + ip);
                  }
              });
          }
docs: via: https://github.com/diafygi/webrtc-ips