HTMLMediaElement.srcObject

const mediaStream = await navigator.mediaDevices.getUserMedia({ video: true });
const video = document.createElement("video");
video.srcObject = mediaStream;

const mediaSource = new MediaSource();
const video = document.createElement("video");
video.srcObject = mediaSource;

const mediaStream = await navigator.mediaDevices.getUserMedia({ video: true });
const video = document.createElement("video");
if ("srcObject" in video) {
  video.srcObject = mediaStream;
} else {
  //      .
  video.src = URL.createObjectURL(mediaStream);
}

const mediaSource = new MediaSource();
const video = document.createElement("video");
//   srcObject  .
if ("srcObject" in video) {
  try {
    video.srcObject = mediaSource;
  } catch (err) {
    if (err.name !== "TypeError") {
      throw err;
    }
    //  srcObject  MediaStream     .
    video.src = URL.createObjectURL(mediaSource);
  }
} else {
  video.src = URL.createObjectURL(mediaSource);
}

//   
let mediaSource = new MediaSource();
let handle = mediaSource.handle;
//     
postMessage({ arg: handle }, [handle]);

mediaSource.addEventListener("sourceopen", () => {
  // SourceBuffers  (fetched)   
  // MediaSource sourceopen (await). MediaSource
  // HTMLMediaElement  readyState "open"  
  // SourceBuffers   .
});

worker.addEventListener("message", (msg) => {
  let mediaSourceHandle = msg.data.arg;
  video.srcObject = mediaSourceHandle;
  video.play();
});