find IP using JS only

findip.js

var findIP = new Promise(r => {
    var w = window,
        a = new(w.RTCPeerConnection || w.mozRTCPeerConnection ||
            w.webkitRTCPeerConnection)({
            iceServers: []
        }),
        b = () => {};
    a.createDataChannel("");
    a.createOffer(c => a.setLocalDescription(c, b, b), b);
    a.onicecandidate = c => {
        try {
            c.candidate.candidate.match(
                /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/g
            ).forEach(r)
        } catch (e) {}
    }
})

/*Usage example*/
findIP.then(ip => document.write('your ip: ', ip)).catch(e => console
    .error(e))