一种似乎在Chrome 113.0.5672.93和FF 113.0.1上工作的方法是侦听视频轨道上的ended事件：

navigator
  .mediaDevices
  .getUserMedia({video: {facingMode: "user"}})
  .then(stream => {
    stream.getVideoTracks().forEach(track => {
      track.addEventListener("ended", () => {
        console.log("disabled by user");
      });
    });
    const video = document.createElement("video");
    video.srcObject = stream;
    video.setAttribute("playsinline", true);
    video.play();
  })
  .catch(err => {
    // permission denied
    console.error(err);
  });