The HTMLLabelElement.htmlFor property reflects the value of the for content property.

The :empty selector refers only to child nodes, not input values. [value=""] does work; but only for the initial state. This is because a node's value attribute (that CSS sees), is not the same as the node's value property (Changed by the user or DOM javascript, and submitted as form data).

I'm looking at https://html.spec.whatwg.org/#attributes-3 right now, and it seems that there are a few others that ought to be boolean but are not currently in this list: allowpaymentrequest, formnovalidate, hidden (is on the original list in the master branch), itemscope, nomodule, and playsinline.

This is a boolean attribute: the presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

Shorthand attributes It's not uncommon to have an attribute where the name and value are the same, like src={src}. Svelte gives us a convenient shorthand for these cases: <img {src} alt="A man dances.">

"Element" SelectorsEach component has a data-reach-* attribute on the underlying DOM element that you can think of as the "element" for the component.