Ignoring capitals?

JavaScript
1

Im getting
image

but the source code is
image
but the insector shows

image
image737Ă—379 24.8 KB

Do the custom tag attributes turn to all lowercase?

2

You’re getting the error because there is a problem with your HTML:

<button class="btn btn-outline-light btn-sm" openRegisterModal">

That trailing quote after openRegisterModal" makes the attribute malformed. As a result, the browser ignores it, and it doesn’t appear in the DOM at all, so any selector fails.

Fix it like this:

<button class="btn btn-outline-light btn-sm" openRegisterModal>

or:

<button class="btn btn-outline-light btn-sm" openregistermodal="true">

While modern browsers will lowercase attribute names when parsing HTML (you can see this in the DOM inspector), selector matching is actually case-sensitive per the spec—so potentially [openRegisterModal] may fail where [openregistermodal] would succeed: https://html.spec.whatwg.org/multipage/semantics-other.html#selectors