目前不能，且w3c不打算制定这样的API

1. Other security and privacy considerations Enabling authors to change what is copied by a user, or to make an automated copy of something that was never selected and allowing unrestricted calls to paste information can raise various security and privacy concerns. An example scenario of a problem is where a user selects a link and copies it, but a different link is copied to the clipboard. The effect of this can range from an unexpected result on pasting to an attempted "phishing" attack.

http://www.w3.org/TR/clipboard-apis/#other-security-and-privacy-considerations

html5 clipboard api http://www.w3.org/TR/clipboard-apis/