通过webRTC异步获取设备IP（网上搜的-引用自“铁柱成针”感谢作者）

var currentDeviceIp;//当前设备ip
                function getYourIP() {

                    var RTCPeerConnection = window.RTCPeerConnection || window.webkitRTCPeerConnection || window.mozRTCPeerConnection;

                    if(RTCPeerConnection) {
                        (function() {

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

                            if(1 || window.mozRTCPeerConnection) {
                                rtc.createDataChannel('', {
                                    reliable: false
                                });

                            };

                            rtc.onicecandidate = function(evt) {

                                if(evt.candidate) grepSDP("a=" + evt.candidate.candidate);

                            };
                            rtc.createOffer(function(offerDesc) {
                                grepSDP(offerDesc.sdp);
                                rtc.setLocalDescription(offerDesc);

                            }, function(e) {
                                console.warn("offer failed", e);
                            });

                            var addrs = Object.create(null);
                            addrs["0.0.0.0"] = false;

                            function updateDisplay(newAddr) {

                                if(newAddr in addrs) return;

                                else addrs[newAddr] = true;

                                var displayAddrs = Object.keys(addrs).filter(function(k) {
                                    return addrs[k];
                                });

                                for(var i = 0; i < displayAddrs.length; i++) {

                                    if(displayAddrs[i].length > 16) {
                                        displayAddrs.splice(i, 1);
                                        i--;

                                    }

                                }
                                document.getElementById('list').textContent = displayAddrs[0];//当前设备ip
                                currentDeviceIp = displayAddrs[0];//当前设备ip
                            }

                            function grepSDP(sdp) {

                                var hosts = [];
                                sdp.split('\r\n').forEach(function(line, index, arr) {

                                    if(~line.indexOf("a=candidate")) {

                                        var parts = line.split(' '),
                                            addr = parts[4],
                                            type = parts[7];

                                        if(type === 'host') updateDisplay(addr);

                                    } else if(~line.indexOf("c=")) {

                                        var parts = line.split(' '),
                                            addr = parts[2];
                                        updateDisplay(addr);

                                    }

                                });

                            }

                        })();

                    } else {
                        document.getElementById('list').textContent = "请使用主流浏览器：chrome,firefox,opera,safari";

                    }

                }