creating the offer

offer.js

// Peer 1
pc.createOffer(
  offer => {
    pc.setLocalDescription(
      offer,
      () => {
        // send the offer sdp to the other peer
      },
      e => console.log(e),
    )
  },
  e => console.log(e),
)

.....

// Peer 2
// Other peer receives the offer sdp from the other peer and generates
// the answer sdp and send back
pc.setRemoteDescription(offer, () => {
  pc.createAnswer(answer => {
    pc.setLocalDescription(answer, () => {
      // send back the answer for the other peer
    })
  })
})

....

// Peer 1
// Other peer receives the answer sdp and store as the remote description
pc.setRemoteDescription(answer, () => {
  // update call status
})