A Use Case for a Parent Selector

Having a “parent selector” in CSS is mentioned regularly as something CSS could really use. I feel like I’ve had that thought plenty of times myself, but then when I ask my brain for a use case, I find it hard to think of one. Well, I just had one so I thought I’d document it here.

A classic parent/child:

<div class="parent">
  <div class="child"></div>
</div>

Say it makes a lot of sense for this parent to have hidden overflow and also for the child to use absolute positioning.

.parent {
   overflow: hidden;
   position: relative;
}

.child {
   position: absolute; 
}

Now let’s say there’s one special circumstance where the child needs to be positioned outside the parent and still be visible. Hidden overflow is still a good default for the vast majority of situations, so it’s best to leave that rule in place, but in this very specific situation, we need to override that overflow.

.special-child {
   position: absolute; 
   bottom: -20px; /* needs to be slightly outside parent */
}

/* Not real, but just to make a point */
.special-child:parent(.parent) {
   overflow: visible;
}

That selector above is fake but it’s saying, “Select the parent of .special-child,” which would allow that override as needed. Maybe it’s like this:

.parent < .special-child {

}

…which is selecting the element on the left rather than the right. Who knows? Probably both of those are problematic somehow and the final syntax would be something else. Or maybe we’ll never get it. I have no idea. Just documenting a real use case I had.

You might be thinking, “Why not just use another special class on the parent?” I would have, but the parent was being injected by a third-party library through an API that did not offer to add a class of my choosing on it. Ultimately, I did have to add the class to the parent by writing some custom JavaScript that queried the DOM to find the .special-child, find the parent, then add the class there.

Do y’all have some other use-cases for a parent selector?

---

Here’s one from Uzair Hayat:

My project has an <input> which is wrapped in a<div>. The <div> has a few design elements which need to take effect once the <input> is in :focus. I could have used ::before and ::after pseudo-elements, but inputs do not support those as they are replaced elements. Right now, I juse JavaScript to detect if the input is in focus and apply a class to the parent div. I wish I could do…

input:focus:parent(div):after {
    display: block;
    /* display design changes when focused */
}