https://caniuse.com/mdn-api_htmloutputelement_setcustomvalidity
HTMLOutputElement API: setCustomValidity | Can I use... Support tables for HTML5, CSS3, etc
"Can I use" provides up-to-date browser support tables for support of front-end web technologies on desktop and mobile web browsers.
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLOutputElement/htmlFor
HTMLOutputElement: htmlFor property - Web APIs | MDN
The read-only htmlFor property of the HTMLOutputElement returns a live DOMTokenList object containing a list of ids of those elements contributing input values...
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