CSS: Use createElementNS to support XSLT documents by apoorvdarshan · Pull Request #5775 · jquery/jquery

apoorvdarshan · 2026-02-18T10:21:22Z

Summary

In XSLT-transformed documents, document.createElement("div").style is undefined because elements are created in the XML namespace rather than XHTML
Changed document.createElement to document.createElementNS("http://www.w3.org/1999/xhtml", ...) in src/css/finalPropName.js and src/css/support.js so that .style is always available
This is the fix recommended in the original issue discussion

Files changed

src/css/finalPropName.js — emptyStyle element creation now uses XHTML namespace
src/css/support.js — table, col, tr, td element creation now uses XHTML namespace (the table.style guard on line 19 already existed, but the root cause is the same)

How to reproduce the original bug

Load a page via in-browser XSLT transformation
In the console: document.createElement("div").style → undefined
Compare: document.createElementNS("http://www.w3.org/1999/xhtml", "div").style → CSSStyleDeclaration

In XSLT-transformed documents, document.createElement("div").style is undefined because elements are created in the XML namespace rather than XHTML. Using document.createElementNS with the XHTML namespace ensures .style is always available. Ref jquerygh-4730

linux-foundation-easycla · 2026-02-18T10:21:28Z

The committers listed above are authorized under a signed CLA.

✅ login: apoorvdarshan / name: Apoorv Darshan (01e100c, 55b4fb6, 57622df, 92aac5b)

mgol

Thanks for the PR. However, source changes are just a small part of what would be required to support XML documents, even on a basic level.

See my comment at #4730 (comment). Some infrastructure parts have changed, but you'd still need to modify mock.php & mockserver.js to support serving true XML documents and then define a few tests using them via testIframe. You can look at some tests already using testIframe to see how to use it; focus on the ones that pass mock.php?action=... as the URL.

Also, we have many more document.createElement usage, it seems we should replace them all? Or maybe create file ./src/var/createElement.js that would wrap the namespace logic? That'd also require measuring the size impact in both cases (running the build locally will tell you the sizes & the diff from a previous build).

Would you like to try that?

- Create src/var/createElement.js that wraps createElementNS with the XHTML namespace to support XSLT/XML documents where document.createElement creates elements without .style - Replace all document.createElement calls in src/ with the helper - Add mock server action (xmlCss) to serve XHTML as application/xml - Add testIframe test verifying jQuery CSS works in XML documents Size impact (minified): -170 bytes, gzipped: -6 bytes The repeated namespace URI string is now centralized in one place. Ref jquerygh-4730

apoorvdarshan · 2026-02-18T20:27:47Z

Thanks for the review @mgol! I've pushed a follow-up commit addressing your feedback:

Changes

Created src/var/createElement.js helper — Wraps document.createElementNS("http://www.w3.org/1999/xhtml", tag) so the namespace logic is centralized in one place.
Replaced all document.createElement calls in src/ with the new helper:
- src/ajax.js — 2 calls (anchor elements for URL parsing)
- src/css/finalPropName.js — 1 call (was already using inline createElementNS)
- src/css/support.js — 4 calls (were already using inline createElementNS)
Added XML document test via testIframe — Serves an XHTML page as application/xml through a new xmlCss mock action (added to both mock.php and middleware-mockserver.cjs). The test verifies:
- document.createElement("div").style is indeed undefined in the XML context (confirming the bug condition)
- jQuery.css("width") still works correctly (confirming our fix)

Size impact

	Before	After	Diff
jquery.js	256,155	256,282	+127
jquery.min.js	78,931	78,761	-170
jquery.min.js (gzip)	27,639	27,633	-6

The minified size actually decreased because the repeated "http://www.w3.org/1999/xhtml" namespace string is now only in one place.

All CSS, ajax, and support tests pass on both Chrome and Firefox.

mgol · 2026-02-18T21:34:29Z

The size impact table is comparing with the previous iteration, right? Against main it's a size increase:

main @7aa0179514a2aa9e1d90fbc6a4b332b8f1ae1292
   raw     gz     br Filename
   -17    +33    +20 dist/jquery.min.js
    +9    +40    +57 dist/jquery.slim.min.js
   -17    +34    +66 dist-module/jquery.module.min.js
    +9    +40    -27 dist-module/jquery.slim.module.min.js

apoorvdarshan · 2026-02-18T21:45:02Z

You're right, the size table was comparing against the previous commit which already had inline createElementNS calls, not against main. Against main it's a net size increase as you showed. Thanks for clarifying!

test/data/css/xmlDocument.xhtml

src/ajax.js

Address review feedback: - Remove redundant comment from xmlDocument.xhtml - Use single var declaration in test scripts - Wrap test code in try-catch, pass `threw` to startIframeTest - Add XML document test for ajax cross-domain detection (jquerygh-4730) Ref jquerygh-4730

apoorvdarshan · 2026-02-18T22:01:58Z

Pushed a follow-up commit addressing the review feedback:

Removed redundant comment from xmlDocument.xhtml
Single var declaration in test scripts instead of multiple var statements
Wrapped test code in try-catch, passing a threw parameter to startIframeTest so the test doesn't hang if jQuery crashes without the fix
Added ajax cross-domain detection test (mock.php?action=xmlAjax) -- verifies that in an XML document, same-origin URLs are detected as same-origin and cross-origin URLs are detected as cross-domain

test/data/css/xmlDocument.xhtml

test/data/css/xmlDocCss.xhtml

src/var/createElement.js

- Uninitialized vars first, initialized last per style guide - Drop empty line between assignments in CSS test - Rename xmlDocument.xhtml to xmlDocCss.xhtml and xmlDocCrossDomainDetection.xhtml for unique names - Update createElement.js comment to reference XML documents generally, not just XSLT Ref jquerygh-4730

apoorvdarshan · 2026-02-19T06:29:25Z

Pushed another commit addressing the latest feedback:

Var ordering - uninitialized vars first, initialized (threw = false) last, applied to both test pages
Dropped empty line between assignments in CSS test page
Renamed files - xmlDocCss.xhtml and xmlDocCrossDomainDetection.xhtml for unique names
Updated createElement.js comment to reference XML documents generally, not just XSLT

mgol

Thanks! This LGTM. I would not backport it to the 3.x-stable line as it has enough additional support tests that may cause more issues.

I want to discuss it with the team before merging, though, so please wait a bit more.

BTW, did you use AI to help with making the changes? I don't mind either way as the changes are high-quality and all my feedback was addressed; in the past, we've had issues with AI-submitted contributions that didn't make any sense, so that'd be the first for me here.

apoorvdarshan · 2026-02-19T10:29:04Z

Thanks for the review! Happy to wait for the team discussion.

And yes, I used Claude Code (Opus 4.6) to assist with the changes.

mgol · 2026-02-23T21:58:06Z

Landed, thanks!

mgol requested changes Feb 18, 2026

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mgol reviewed Feb 18, 2026

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mgol added the Discuss in Meeting Reserved for Issues and PRs that anyone would like to discuss in the weekly meeting. label Feb 18, 2026

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gibson042 approved these changes Feb 23, 2026

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timmywil approved these changes Feb 23, 2026

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mgol added this to the 4.1.0 milestone Feb 23, 2026

mgol merged commit dcb31ae into jquery:main Feb 23, 2026
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apoorvdarshan commented Feb 18, 2026

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apoorvdarshan commented Feb 18, 2026 •

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