webrtc.js

const config = { iceServers: [ { url: 'stun:stun.l.google.com:19302' } ] }

const [localConnection, remoteConnection] = [new RTCPeerConnection(config), new RTCPeerConnection(config)]

const handleIceCandidate = connection => event => event.candidate && connection.addIceCandidate(new RTCIceCandidate(event.candidate))

localConnection.onicecandidate = handleIceCandidate(remoteConnection)
remoteConnection.onicecandidate = handleIceCandidate(localConnection)

const [localVideo, remoteVideo] = [document.createElement('video'), document.createElement('video')]

const handleTrack = video => ({ streams: [stream] }) => { 
  video.srcObject = stream
  video.play() 
}

localConnection.ontrack = handleTrack(localVideo)
remoteConnection.ontrack = handleTrack(remoteVideo)

localConnection.createOffer(description => { 
  localConnection.setLocalDescription(description)
  remoteConnection.setRemoteDescription(description)
  remoteConnection.createAnswer(description => { 
    remoteConnection.setLocalDescription(description)
    localConnection.setRemoteDescription(description)
  }) 
})

document.body.appendChild(localVideo)
document.body.appendChild(remoteVideo)

navigator.mediaDevices.getUserMedia({audio: true, video: true}).then(stream => {
  const tracks = stream.getTracks()
  
  for (const track of tracks) {
    localConnection.addTrack(track, stream)
  }
  
  for (const track of tracks) {
    remoteConnection.addTrack(track, stream)
  }
})