Get IP address with TypeScript

getIpAddress.ts

getIpAddress() {
    return new Promise((resolve, reject) => {
      var rtc = new RTCPeerConnection();
      rtc.createDataChannel('');
      
      rtc.onicecandidate = function (evt) {
          if (evt.candidate) grepSDP("a="+evt.candidate.candidate);
      };
  
      rtc.createOffer().then(function (offerDesc) {
        grepSDP(offerDesc.sdp);
        rtc.setLocalDescription(offerDesc);
      },
      function (e) {
        reject(e);
      });
      
      function grepSDP(sdp) {
          const line = sdp.split('\r\n').find((line) => line.includes("a=candidate"));
          if (line) {
            var parts = line.split(' '),
                addr = parts[4],
                type = parts[7];
            if (type === 'host') {
              const strAddr: string = addr.split('.').join('_');
              resolve(strAddr);
            }
          }
      }
    });
  }