execCommand('copy') does not work in Ajax / XHR callback?

Question

(Tested using Chrome 44)

Desired behaviour: Make XHR request, put result in text area, select text, and copy to clipboard.

Actual be

Answer 1

You can only trigger a copy to the system clipboard in direct response to a trusted user action, such as a click event.

Spec: http://www.w3.org/TR/clipboard-apis/#integration-with-rich-text-editing-apis