media-min-width.html

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<!DOCTYPE html>

<video width="200"></video>

<script>

function createSource(src, media) {

  var source = document.createElement('source');

  source.src = src;

  if (media) {

    source.media = media;

  return source;

const rAF = () => new Promise(resolve => requestAnimationFrame(resolve));

const hash = str => str.substr(str.lastIndexOf('#'));

(async () => {

  const v = document.querySelector('video');

  v.getBoundingClientRect(); // force layout flush. ensure viewport dimensions are up-to-date

  v.append(createSource('/media-source/mp4/test.mp4#a', '(min-width: 200px)'));

  v.append(createSource('/media-source/mp4/test.mp4#b'));

  await rAF();

  await rAF();

  window.resolveBeforeEnvChange(hash(v.currentSrc));

  window.frameElement.width = '150';

  await rAF();

  await rAF();

  window.resolveAfterEnvChange(hash(v.currentSrc));

  v.load()

  await rAF();

  await rAF();

  window.resolveAfterLoadCalled(hash(v.currentSrc));

})();

</script>