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The type of Document.documentElement could be SVGSVGElement #29052

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EFanZh opened this issue Dec 16, 2018 · 4 comments
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The type of Document.documentElement could be SVGSVGElement #29052

EFanZh opened this issue Dec 16, 2018 · 4 comments
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Revisit An issue worth coming back to Suggestion An idea for TypeScript

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@EFanZh
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EFanZh commented Dec 16, 2018 •
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Currently, the type of Document.documentElement is HTMLElement:

https://github.com/Microsoft/TypeScript/blob/4d74f67325d305f52a2b00b4f30b5a4f3210c649/lib/lib.dom.d.ts#L4124

But it is possible for a Document’s documentElement property to be of type SVGSVGElement which is not a subtype of HTMLElement:

Try to run the following code:

const d = (new DOMParser()).parseFromString('<svg xmlns="http://www.w3.org/2000/svg"></svg>', 'image/svg+xml');
const k = (d instanceof Document) && (d.documentElement instanceof SVGSVGElement);

the value of k should be true.

Also, why isn’t there a SVGDocument in TypeScript?
@AnyhowStep
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AnyhowStep commented Dec 16, 2018 •
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Probably because it's usually used with HTML and not anything else that isn't HTML. And HTML should have the <html> tag as the root element.

You can pretty much have any XML tag be the documentElement.

Might be oversight. Might be deliberate after weighing correctness vs. ease of the "usual" use case

@nmain
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nmain commented Dec 17, 2018

This can probably be subsumed by #4689. Although originally about parentElement, discussion in that ticket includes documentElement as well.

@weswigham
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AFAIK we know this and override the Element base type with HTMLElement because most usages are with the DOM's document.

@weswigham weswigham added Suggestion An idea for TypeScript Revisit An issue worth coming back to labels Dec 17, 2018
@lydell lydell mentioned this issue Sep 22, 2019
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@MartinJohns MartinJohns mentioned this issue Jul 28, 2022
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@AGluk AGluk mentioned this issue Sep 8, 2023
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@AGluk
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AGluk commented Sep 8, 2023

I think that documentElement should be just Element.
Then it can be used as HTMLElement or SVGSVGElement.

@aayla-secura aayla-secura mentioned this issue Dec 22, 2024
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@EFanZh @weswigham @AnyhowStep @AGluk @nmain