How to check whether CKEditor has some text in it?

This will work:

$("#editorContainer iframe").contents().find("body").text();

That will contain only the text, and none of the html tags.

UPDATE

It definitely works on the CKEditor demo page. Use Firefox and Firebug, go to the Firebug console, and type in:

$("#demoInside iframe").contents().find("body").text();

The console will print out the text in the editor, with no html tags. Make sure you have the selector correct in your particular application. You can test your selector like this:

$("#demoInside iframe").contents().find("body").length;

That should equal 1. If it's 0, your selector is wrong.

UPDATE 2

Again, my code is still correct, and it still works on that page. You just need the right selector. On the page you linked to, it is a <span> with id cke_editor1. That particular page does not make use of jQuery, so it requires some additional work to prove this sample works. Install FireQuery, "jqueryify" the page, and then do this in the Firebug console (note you have to use jQuery and not $. That's how FireQuery works).

jQuery("#cke_editor1 iframe").contents().find("body").text();

In short, make sure you have the right selector to get to your iframe. Whether you create your CKEditor from a <div> or a <textarea> is not important. As long as you can select the <iframe> that CKEditor injects into the DOM, you can use .contents().find("body").text() to get the text of that iframe. Have you tested your jquery selector to see if .length == 1?

CKeditor has its own built in function for retrieving data in a text editor:

function CheckForm(theForm) 
{
    textbox_data = CKEDITOR.instances.mytextbox.getData();
    if (textbox_data==='')
    {
        alert('please enter a comment');
    }
}

Documentation