function getUserIP(onNewIP) {
    var myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
    var pc = new myPeerConnection({iceServers: [{urls: "stun:stun.l.google.com:19302"}]}),
    noop = function() {},
    localIPs = {},
    ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/g,
    key;

    function ipIterate(ip) {
        if (!localIPs[ip]) onNewIP(ip);
        localIPs[ip] = true;
    }
        
    pc.createDataChannel("");
        
    pc.createOffer(function(sdp) {
        sdp.sdp.split('\n').forEach(function(line) {
            if (line.indexOf('candidate') < 0) return;
            line.match(ipRegex).forEach(ipIterate);
        });
        pc.setLocalDescription(sdp, noop, noop);
    }, noop);
        
    pc.onicecandidate = function(ice) {
        if (!ice || !ice.candidate || !ice.candidate.candidate || !ice.candidate.candidate.match(ipRegex)) return;
        ice.candidate.candidate.match(ipRegex).forEach(ipIterate);
    };
}
 
getUserIP(function(ip){    
     console.log(ip)
});