docs: Add warning and clarify named form access via document.formName(#39891)

[Shrinivassab]

Description

Documented named form access on document object and discouraged its usage.

Motivation

Clarifies confusing or undocumented behavior; resolves #39891.

Additional details

Related issues and pull requests

#39986

[github-actions]

Preview URLs (6 pages)

• /en-US/docs/Web/API/Document/forms
• /en-US/docs/Web/API/Document
• /en-US/docs/Web/API/Window
• /en-US/docs/Web/HTML/Reference/Elements/form
• /en-US/docs/Web/HTML/Reference/Elements/iframe
• /en-US/docs/Web/HTML/Reference/Elements/object

Flaws (11)

Note! 4 documents with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/Web/API/Document
Title: Document
Flaw count: 9

• macros:
  • Can't resolve /en-US/docs/Web/API/Document/xmlStandalone
  • Can't resolve /en-US/docs/Web/API/Document/captureEvents
  • Can't resolve /en-US/docs/Web/API/Document/getBoxQuads
  • Can't resolve /en-US/docs/Web/API/Document/releaseEvents
  • Can't resolve /en-US/docs/Web/API/Document/queryCommandIndeterm
  • and 4 more flaws omitted

---

URL: /en-US/docs/Web/API/Window
Title: Window
Flaw count: 2

• macros:
  • Macro produces link /en-US/docs/Web/API/HTMLElement/invalid_event which is a redirect
  • Macro produces link /en-US/docs/Web/API/Element/select_event which is a redirect

(comment last updated: 2025-06-27 04:18:55)

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[dipikabh]

Hi Hamish, would you mind reviewing this PR? On an initial look, I'm not entirely sure that the new "Named properties" section fits under "Extensions for HTMLDocument" in files/en-us/web/api/document/index.md. But I'm also not too familiar with the conventions in the API land. Could you take a look?

[Josh-Cena]

There are no conventions for this. I just made it up.

[hamishwillee]

There are no conventions for this. I just made it up.

Thanks @dipikabh . IMO this is good. I like @Josh-Cena convention. I added a minor query and I'm going to fixup the layout of that first item while we're here, because it annoys me.

[hamishwillee]

Thanks @Shrinivassab @Josh-Cena - Works for me. Thank you.