How can I write a text to a question whenever the page is not on focus?

Pei_2009

I want to record the timestamp whenever the page is out of focus. I made a text entry question in the end of the page. It did not work. Can anyone help to fix it? The ideal case is that a new moment the page is out of focus, I will add/append a string of date time as a text to the question answer.

TomG

See: https://stackoverflow.com/a/1060034/4434072