var canvas = document.querySelector("canvas");

// Optional frames per second argument.
var stream = canvas.captureStream(25);
var recordedChunks = [];

console.log(stream);
var options = { mimeType: "video/webm; codecs=vp9" };
mediaRecorder = new MediaRecorder(stream);

mediaRecorder.ondataavailable = handleDataAvailable;
mediaRecorder.start();

function handleDataAvailable(event) {
  console.log("data-available");
  if (event.data.size > 0) {
    recordedChunks.push(event.data);
    console.log(recordedChunks);
    download();

  } else {
    // ...
  }
}
function download() {
    var blob = new Blob(recordedChunks, {
      type: 'video/webm'
    });
    var url = URL.createObjectURL(blob);
    var a = document.createElement('a');
    document.body.appendChild(a);
    a.style = 'display: none';
    a.href = url;
    a.download = 'test.webm';
    a.click();
    window.URL.revokeObjectURL(url);
  }

//for logging status
setInterval( (event) => {

    console.log(mediaRecorder);

},1500);

// demo: to download after 9sec
setTimeout( (event) => {
    console.log("stopping");
    mediaRecorder.stop();
}, 9000);