The copy
event fires when the user initiates a copy action through the browser's user interface.
The event's default action is to copy the selection (if any) to the clipboard.
A handler for this event can modify the clipboard contents by calling setData(format, data)
on the event's ClipboardEvent.clipboardData
property, and cancelling the event's default action using event.preventDefault()
.
However, the handler cannot read the clipboard data.
It's possible to construct and dispatch a synthetic copy
event, but this will not affect the system clipboard.