Inserting Value To AjaxControlToolkit - HTMLEditor Using Javascript?

I'm using AjaxControlToolkit.HTMLEditor, and I want to add value to it using javascript or jquery like this:

alert( $find("eCompose_ctl02_ctl01")); // if

$find("eCompose_ctl02_ctl01").attr('value') = "asdfasdfasdf asdfasd asdf sf";

also tried like this:

document.getElementById('eCompose_ctl02_ctl01').value += "ababsakas asdasd l";

But the above code does not insert text into HTMLEditor.

EDIT.this is html code for HTMLEditor:

<HTMLEditor:Editor ID="eCompose" runat="server" Height="240px" Width="90%" AutoFocus="true" InitialCleanUp="true" />

i tried to access like this: alert(document.getElementById("<%= eCompose.ClientID %>")) and got null