There isn't a definite list, it's up to the browser. The only standard we have is DOM Level 2 HTML, according to which the only elements that have a focus()
method are
HTMLInputElement
, HTMLSelectElement
, HTMLTextAreaElement
and HTMLAnchorElement
. This notably omits HTMLButtonElement
and HTMLAreaElement
.
Today's browsers define focus()
on HTMLElement, but an element won't actually take focus unless it's one of:
- HTMLAnchorElement/HTMLAreaElement with an href
- HTMLInputElement/HTMLSelectElement/HTMLTextAreaElement/HTMLButtonElement but not with
disabled
(IE actually gives you an error if you try), and file uploads have unusual behaviour for security reasons
- HTMLIFrameElement (though focusing it doesn't do anything useful). Other embedding elements also, maybe, I haven't tested them all.
- Any element with a
tabindex
There are likely to be other subtle exceptions and additions to this behaviour depending on browser.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…