I have a simple form that uploads an invoice as part of the required information.  I would like the invoice to immediately display within the form for quick reference without having to open the document.  So, basically, as soon as the form is uploaded, the image would be displayed within the form.

I am new to scripting, so I struggle writing code.  Does anyone have a code, or at least some reference guides that may help me? 

I got this code at one of the courses at the conference, but I am not sure how to customize it to my situation.  The first part detects a file upload, and the second part is supposed to display it.