HTML nodeName and tagName properties of nodes are in upper case

[domleonard]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement

What specific section or headline is this issue about?

https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement#parameters - tagName

What information was incorrect, unhelpful, or incomplete?

While nodeName and tagName are held in DOM nodes of HTML pages in upper case, description for the tagName parameter states the opposite:

When called on an HTML document, createElement() converts tagName to lower case before creating the element.

What did you expect to see?

When called on an HTML document, createElement() converts tagName to upper case before creating the element.

Do you have any supporting links, references, or citations?

console.log(document.querySelector('html').tagName);

Do you have anything more you want to share?

No response

MDN metadata

Page report details

• Folder: en-us/web/api/document/createelement
• MDN URL: https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement
• GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/api/document/createelement/index.md
• Last commit: dcbb1d9
• Document last modified: 2024-09-24T13:57:44.000Z

[Josh-Cena]

This is consistent with the HTML spec https://dom.spec.whatwg.org/#dom-document-createelement:

If this is an HTML document, then set localName to localName in ASCII lowercase.

tagName is the odd one here, not createElement. All intrinsic elements are lowercase, but tagName and nodeName uppercases them specifically before returning it. You can observe the lowercase tag name via any other method, such as the browser's devtools.

[wbamberg]

I looked at this and had a similar thought, but the use of tagName here instead of localName is very confusing, and I suggest we change that.

[Josh-Cena]

Agreed, let's use localName instead.