It would be useful with a client side logging solution written entirely in javascript.  With Html5 comes a client side database.  Already today we have cookies that could be used.

Logging could be done  in a round robin fashion where old logs are dropped so one always keeps the latest x logs in the database/cookie.  One could also send thelog back to the server if needed.

That way we wouldn’t need alert calls.  Especially forgotten alert calls that goes into production.