How to get editor content via JavaScript?

I need to access the contents of the editor via javascript. The reason is that I am using the editor in a pop-up window and want to update a field in the parent window when submitting (instead of submitting).

opener.document.form1.<%=parentField%>.value = document.FCKEditor_Field.value;

So, what do I replace "FCKEditor_Field" with in order to get the current html value?

Thank you!