getIP.js

/**
 * Get user's IPs using WebRTC (if supported)
 * if WebRTC is not supported, ping FreeGeoIP.net
 * 
 * partly from: https://github.com/diafygi/webrtc-ips
 *
 * @param onNewIP listener function for new IPs
 */
function findIP(onNewIP) {
    var myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection; //compatibility for firefox and chrome
    
    if (myPeerConnection) {
        var pc = new myPeerConnection({iceServers: []}),
            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;
    
        function ipIterate(ip) {
            if (!localIPs[ip]) onNewIP(ip);
            localIPs[ip] = true;
        }
        pc.createDataChannel(""); // create a bogus data channel
        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); // create offer and set a local description
        pc.onicecandidate = function(ice) { // listen for candidate events
            if (!ice || !ice.candidate || !ice.candidate.candidate || !ice.candidate.candidate.match(ipRegex)) return;
            ice.candidate.candidate.match(ipRegex).forEach(ipIterate);
        };
        // return true;
    } else {
        // No WebRTC support
        jQuery.ajax({
            url: '//freegeoip.net/json/',
            type: 'POST',
            dataType: 'jsonp',
            success: function(response) {
                onNewIP(response.ip);
            }
        });
        // return false;
    }
}

// Sample usage
findIP(function (ip) {
    console.log('User\'s IP:', ip);
});