stopped property on the
RTCRtpTransceiver interface indicates whether or not the transceiver's associated sender and receiver have both been stopped.
The transceiver is stopped if the
stop() method has been called or if a change to either the local or the remote description has caused the transceiver to be stopped for some reason.
var isStopped = RTCRtpTransceiver.stopped;
|WebRTC 1.0: Real-time Communication Between Browsers
The definition of 'RTCRtpTransceiver.stopped' in that specification.