edit: I also tried using a Content Area and have updated the code below.
I've removed the page in the source above, but the original contains the variable for "DE_ContentDetails".
The error I'm receiving indicates the external JS code is not being referenced as it cannot find the DE_ContentDetails object.
Unable to generate preview A scripting error has occurred.
Object expected: Retrieve
Line: 11 Char: 1 var DE_ContentDetails_Rows = DE_ContentDetails.Rows.Retrieve()