How to check whether CKEditor has some text in it?

I have an HTML form with a few fields. One of them is a textarea managed by CKEditor.

When the user wants to submit the form, I want to check whether he entered values in all the fields.

I know how I can check if CKEditor control has anything in it, but it could be "empty" HTML tags without any text in it.

How do I check for text?

Server side I'm using something like PHP's trim(strip_tags($content)), so I'd like to have the same in JavaScript.

A solution using jQuery would also be usable.