Is there a reliable way to show Drupal messages from JavaScript? I need to show status messages (the kind typically shown by drupal_set_message()) in my module's JavaScript code. How can I do this reliably, such that the theme and placement of the messages remains consistent with the way drupal_set_message() does it?

I'm looking for a solution that accounts for the presence or absence of prior messages on the page, and that works for any theme.

Pointing to existing modules that perform this would be great!
I'm using Nice messages module to replace every message with a popup in the corner of the screen.

https://drupal.org/project/nicemessages

It lets you choose if you want the messages of a status to stay visible until closed, or auto close after x seconds.
And add a handy "close all" if there are more than one.

If anything, check out how it works. It's a good starting point i guess.