Client-Side Equivalent of drupal_set_message with javascript I've got javascript that notifies the user of actions and errors, and I'd like to use the existing Drupal messaging. Is this built in to Drupal?

Alternatively, (I'm fairly new to Drupal and am not very familiar with the modules available) if this is available as a module, I haven't been able to find it. Does anyone know of a module?

UPDATE: To clarify, I'm trying to set a Drupal message from the client-side (JavaScript), on a page that has already rendered. This is a very AJAXy page with tonnes of functionality that sometimes requires messages be shown to the user.

Is there is a provision in the Drupal client-side API for setting messages?
I don't see JS API for dispaying messages even in D7. Maybe because all you need is DIV with classes like messages,status warning or error. You can see how drupal works with it in file /misc/tabledrag.js.
When you drag rows in tables drupal shows you a warning message with this code:

$(Drupal.theme('tableDragChangedWarning')).insertBefore(self.table).hide().fadeIn('slow');