Get Local IP Address from Browser (inspired by net.ipcalf.com)

getLocalIpAddress.js

function getLocalIpAddress() {
	return new Promise(function (resolve, reject) {
		var RTCPeerConnection = window.RTCPeerConnection || window.webkitRTCPeerConnection || window.mozRTCPeerConnection;

		if (RTCPeerConnection) {
      var rtc = new RTCPeerConnection({iceServers: []});

      if (1 || window.mozRTCPeerConnection) {           // FF [and now Chrome!] needs a channel/stream to proceed
        rtc.createDataChannel('', {reliable: false});
      };

      rtc.onicecandidate = function (evt) {
        // convert the candidate to SDP so we can run it through our general parser
        // see https://twitter.com/lancestout/status/525796175425720320 for details
        if (evt.candidate) grepSDP("a="+evt.candidate.candidate);
      };

      rtc.createOffer(function (offerDesc) {
        grepSDP(offerDesc.sdp);
        rtc.setLocalDescription(offerDesc);
      }, function (e) { reject(new Error('WebRTC Offer Failed')) });


      var addrs = Object.create(null);

      var INVALID_ADDR = "0.0.0.0"

      addrs[INVALID_ADDR] = false;

      function grepSDP(sdp) {
        var hosts = [];
        if (sdp) {
          sdp.split('\r\n').forEach(function (line) {   // c.f. http://tools.ietf.org/html/rfc4566#page-39
            if (~line.indexOf("a=candidate")) {           // http://tools.ietf.org/html/rfc4566#section-5.13
                var parts = line.split(' '),              // http://tools.ietf.org/html/rfc5245#section-15.1
                addr = parts[4],
                type = parts[7];
                if (type === 'host' && addr !== INVALID_ADDR) {
                  resolve(addr)
                }
            } else if (~line.indexOf("c=")) {             // http://tools.ietf.org/html/rfc4566#section-5.7
                var parts = line.split(' '),
                addr = parts[2];
                if (addr !== INVALID_ADDR) {
                  resolve(addr)
                }
            }
          });
        }

      }
		} else {
			reject(new Error('WebRTC not supported by this browser'))
		}
	})
}

Done on Firefox but random value on Chrome like : 6f7a1346-ae1b-4ba2-b69c-e01dfc490a24.local