How to record cycled video from shadertoy

shadertoy_exporter.js

// copy paste this in console
function shader_exporter(duration, width, heigth, paused) {
  document.getElementById('demogl').style.width = width + 'px';
  document.getElementById('demogl').style.height = heigth + 'px';
  document.getElementById('myResetButton').click();
  document.getElementById('myRecord').click();
  if (paused) document.getElementById('myPauseButton').click();
  let t0 = performance.now();
  function loop(){
    if (performance.now() - t0 > duration * 1000) {
      document.getElementById('myRecord').click();
      if (paused) document.getElementById('myPauseButton').click();
    } else {
      requestAnimFrame(loop)
    }
  };
  requestAnimFrame(loop);
}
shader_exporter(6.28318530, 512, 512, false);

@munrocket Sorry, I was running this script in Safari which does not support Webm. Works fine in Chrome, thanks!