Multi-line text field length

I would like to check if a multi-line text field is empty using javascript/jquery.

The default field length is 11.  If I trim the spaces, the field still occupies 11 characters.  How can i test the field to be empty?  It contains non displayable characters.  They look like spaces when displayed in an alert but triming the spaces still leaves the value at 11 positions.

If you type something into the field, the first 11 characters take up the 11 default positions.  So the length is always a minimum of 11 characters.  (Even if blank).