The active read-only property of the MediaStream interface returns a Boolean value which is true if the stream is currently active; otherwise, it returns false. A stream is considered active if at least one of its MediaStreamTracks does not have its property MediaStreamTrack.readyState set to ended. Once every track has ended, the stream's active property becomes false.

A Boolean value which is true if the stream is currently active; otherwise, the value is false.

In this example, a new stream whose source is the user's local camera and microphone is requested using getUserMedia(). When that stream becomes available (that is, when the returned Promise is fulfilled, a button on the page is updated based on whether or not the stream is currently active.

const promise = navigator.mediaDevices.getUserMedia({
  audio: true,
  video: true,
});

promise.then((stream) => {
  const startBtn = document.querySelector("#startBtn");
  startBtn.disabled = stream.active;
});