A web page may implement their own key command handling and want to prevent the default browser behavior by calling Event.preventDefault() in their onkeydown handler. For example, a page may implement their own Find-in-page feature that is toggled by listening for Command + F, the same key command to trigger the default browser Find-in-page feature. Calling Event.preventDefault() in their onkeydown handler when they receive Command + F should prevent Safari from showing the Find-in-page UI. But it does not on iOS. It does on Mac.
(In reply to Daniel Bates from comment #0) > A web page may implement their own key command handling and want to prevent > the default browser behavior by calling Event.preventDefault() in their > onkeydown handler. For example, a page may implement their own Find-in-page > feature that is toggled by listening for Command + F, the same key command > to trigger the default browser Find-in-page feature. Calling > Event.preventDefault() in their onkeydown handler when they receive Command > + F should prevent Safari from showing the Find-in-page UI. But it does not > on iOS. It does on Mac. App key commands, like Command + F, should only be prevented from a key press handler to match Mac and the UIEvents spec.
*** This bug has been marked as a duplicate of bug 192897 ***
<rdar://problem/47338324>
<rdar://problem/47338325>