html5页面拨号

<button onclick="makeCall()">拨打</button>

function makeCall() {
  var phoneNumber = document.getElementById("phone").value;
  var session = new RTCPeerConnection();
  session.createOffer()
    .then(offer => session.setLocalDescription(offer))
    .then(() =>
      fetch("/makeCall", {
        method: "POST",
        body: JSON.stringify({
          from: "me",
          to: phoneNumber,
          sdp: session.localDescription.sdp
        })
      })
    )
  .then(response => response.json())
  .then(answer => session.setRemoteDescription(new RTCSessionDescription({
    type: "answer",
    sdp: answer.sdp
  })));
}

<audio id="localAudio" autoplay muted></audio>
<audio id="remoteAudio" autoplay></audio>

session.addTrack(localStream.getAudioTracks()[0]);
session.ontrack = function(event) {
  document.getElementById("remoteAudio").srcObject = event.streams[0];
};