How to get CKEditor TextBox Value in JavaScript or jQuery

I am inserting data using Ajax and javascript. I want to get data of CKEditor contents. I am try to get like below but not getting:

 <%@ Register Assembly="CKEditor.NET" Namespace="CKEditor.NET" TagPrefix="CKEditor" %>

     <CKEditor:CKEditorControl ID="txtContents" Height="400" runat="server" Width="500" onkeypress ="return suppressNonEng(event)"></CKEditor:CKEditorControl>

i am wriiting code to get contents like bvelow: 

 var CEn = document.getElementById('ctl00_ContentPlaceHolder1_txtContents').value;

Please suggest me that how i should write to get the contents of CKEditor in Javascript.