value of alt attribute in image token is empty about markdown-it HOT 2 CLOSED

By CM spec, alt can have markup inside (i know, that's very strange). So, it can't be stored in attr value (those are for plain values). I don't remember full details, but you can dig in image renderer/rule.

from markdown-it.

By CM spec, images are the same as links. This is an example from cmark:

[markup](link "title")
![markup](image "title")

<link destination="link" title="title">
  <text>markup</text>
</link>
<image destination="image" title="title">
  <text>markup</text>
</image>

Then markup gets folded into string at render time. "alt" you see is just a placeholder for where that markup will end up.

from markdown-it.