minify-html/notes/Script data.md

Script data

Summary

For legacy reasons, HTML comments can appear within a script tag, and if there is a <script in it, the first following </script> within the comment does not close the main script tag.

minify-html does not do this special handling, as it adds complexity and slows down performance dramatically, for a legacy feature that is not recommended to be (and almost never) used.

See https://www.w3.org/TR/html52/syntax.html#script-data-state for more details.

Commit 20c59769 removed support.

States and transitions

State	<script	</script	<!--	-->
Normal	-	End	Escaped	-
Escaped	DoubleEscaped	End	-	Normal
DoubleEscaped	-	Escaped	-	Normal

Examples

<script type="text/html">
  <script>
    exec1 = true;
  </script>
  <script>
    exec2 = true;
  </script>
</script>

These are true about the above snippet:

• document.querySelectorAll('script').length === 2.
• !window.exec1 && window.exec2.
• document.querySelector('script[type="text/html"]') has exactly one child node and it's a text node.

If there is one or more <script> inside an HTML comment before any </script>, the first </script> will not end the main script.

Ending tag inside comment works because there are no nested script tags.

<script type="text/plain"><!--
</script>

There is a nested tag but it doesn't need to be closed because it's treated as text.

<script type="text/plain">
  <script>
</script>

There is a nested tag but it doesn't need to be closed because it's not inside an HTML comment.

<script type="text/plain">
  <script><!--
</script>

There is a nested tag but it doesn't need to be closed because main closing tag is not inside an HTML comment.

<script type="text/plain"><!--
  <script>-->
</script>

The main closing tag is in a HTML comment but still works because there is no <script> before it in its comment (there is one in the previous comment).

<script type="text/plain">
    <!--<script>--><!--
</script>

There is a nested tag and it's in an HTML comment but it doesn't need to be closed because it's not script.

<script type="text/plain"><!--
  <div>
</script>

First closing tag is inside a comment with one or more previous opening tags so it doesn't close main script tag.

<script type="text/plain"><!--
  <script>alert();</script>
</script>

There is a nested tag and it needs to be closed because it's in a comment script. The amount of <script> doesn't matter.

<script type="text/plain"><!--
  <script><script><script><script><script>alert();</script>
</script>

First and second closing tags close their respective previous 1+ opening tags.

<script type="text/plain"><!--
  <script><script><script>alert();</script>
  <script></script>
</script>

Main closing tag works because it is in a separate comment.

<script type="text/plain">
  <!--<script><script><script>--><!--
</script>

Main closing tag works because it is not in a comment.

<script type="text/plain">
  <!--<script>-->
</script>