Tristate checkboxes in HTML [duplicate]

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• HTML - Why isn't indeterminate=“indeterminate|true” respected? 2 answers

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I was going through a tutorial on intermediate checkboxes and found that they could only be shown via javascript.

This means that there is no pure HTML way to display something that is essentially a UI state.

So, my question is, is there any particular reason for HTML not to be able to edit a property of an element while Javascript can? Is it an oddity or relatively commonplace?

Also were there any standards in HTML about these intermediate states. I checked the W3 HTML docs but they don't even mention tristates which leads me to believe that it is a browser specific decision