Cannot dynamically set the source tag src attribute for YouTube videos.

[carlod]

When trying to dynamically set the src atttribute, of the source tag, I get a return value of null from getElementById("sourceId"). This is due to the DOM manipulation your framework does when it encounters a wb-mltmd class that creates an IFrame to display the YouTube content. With the source tag removed from the DOM I see no way to dynamically set it,

<figure class="wb-mltmd" >
	<video id="videoId3" src="">
		<source id="sourceId" type="video/youtube" src="https://www.youtube.com/watch?v=Stbi6brWAzA" />
	</video>
	<figcaption class="mrgn-tp-md">
		<details id="inline-captions">
			<summary>Video transcript</summary>
		</details>
	</figcaption>
</figure>

[ghost]

Using the following code I had no issue (there is an unnecessary tag in your HTML <video id="videoId3" src=""> remove src=""):

HTML:

<figure class="wb-mltmd">
  <video id="video" title="YouTube">
		<source id="source" type="video/youtube" src="https://www.youtube.com/watch?v=Stbi6brWAzA" />
	</video>
  <figcaption class="mrgn-tp-md">
    <details id="inline-captions">
      <summary>YouTube</summary>
    </details>
  </figcaption>
</figure>

JavaScript:

const source = document.getElementById("source");
source.src = "http://www.youtube.com/watch?v=9znKJqnFuuY";
source.trigger( "wb-init.wb-mltmd" ); // You'll also need this to reset WET controls