Question

I’m trying to disable the html/body scrollbar of the parent while I’m using a lightbox. The main word here is disable. I do not want to hide it with overflow: hidden;.

The reason for this is that overflow: hidden makes the site jump and take up the area where the scroll was.

I want to know if its possible to disable a scrollbar while still showing it.

Answer 1

If the page under the overlayer can be "fixed" at the top, when you open the overlay you can set

body { 
  position: fixed; 
  overflow-y: scroll;
}

you should still see the right scrollbar but the content is not scrollable. When you close the overlay just revert these properties with

body { 
  position: static;
  overflow-y: auto; 
}

I just proposed this way only because you wouldn’t need to change any scroll event

What if I already scrolled the page?

if you get the document.documentElement.scrollTop property via javascript just before the layer opening, you could dynamically assign that value as top property of the body element: with this approach the page will keep its current scroll position, no matter if you’re on top or if you have already scrolled.

Css

.noscroll {
  position: fixed; 
  top: var(--st, 0);
  inline-size: 100%;
  overflow-y:scroll; 
}

JS

const b = document.body;
b.style.setProperty('--st', -(document.documentElement.scrollTop) + "px");
b.classList.add('noscroll');