The background-attachment CSS 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.