The background-attachment property specifies whether background images are fixed with regard to the viewport (fixed), or scroll along with the element (scroll), or its contents (local).
object.style.backgroundAttachment = "value";
<'background-attachment'> = <attachment>#
<attachment> = scroll | fixed | local
The background is fixed with regard to the element itself.
The background is fixed with regard to the viewport.
The background is fixed with regard to the element's contents.
World Wide Web Consortium (W3C)