⚠️ Deprecated. Use data-oninclude instead.

Previously used to call JavaScript functions to transform element content. Kept for backwards compatibility with very old ReSpec specs.

<!-- Before: -->
<section data-transform="myFunction">...</section>

<!-- After: use data-oninclude for included content -->
<section data-include="content.html"
         data-oninclude="myFunction">
</section>

data-transform called arbitrary global functions (window[functionName]()) on element content, including window.eval. This is why it was deprecated — use data-oninclude which is scoped to included content only.