README

Make a natively horizontal-scrolling element better: drag it with the mouse, add prev/next buttons, and (optionally) play nicely with CSS scroll-snap.

Usage

Start with an element that already scrolls horizontally. For the prev/next buttons to position correctly, wrap it in a relatively positioned element:

<div class="relative">
    <div class="horizontal-scroller">
        <ul class="items">
            <li class="item">Item A</li>
            <li class="item">Item B</li>
            <li class="item">Item C</li>
            <!-- … -->
        </ul>
    </div>
</div>

.relative {
    position: relative;
}
.horizontal-scroller {
    overflow-x: auto;
    overflow-y: hidden;
}
.items {
    list-style: none;
    padding: 0;
    display: flex;
    gap: 40px;
}
.item {
    flex: 0 0 200px;
    padding: 5%;
    background-color: #ddd;
}

Then enhance it:

<script src="horizontal-scroller.js"></script>
<script>
    new HorizontalScroller({
        selector: '.horizontal-scroller',
    });
</script>

Options

All options are optional; the values below are the defaults.

Buttons

The prev/next buttons are injected as empty elements right after the scroller, so you style them yourself. They get the base class plus a -left / -right modifier, and a hide class when the scroller reaches that edge (so you can fade/hide them):

.horizontal-scroller-button {
    position: absolute;
    display: block;
    width: 50px;
    height: 50px;
    top: 50%;
    transform: translateY(-50%);
}
.horizontal-scroller-button-left {
    left: 0;
}
.horizontal-scroller-button-right {
    right: 0;
}
.horizontal-scroller-button.hide {
    display: none;
}

Scroll-snap

Snap works out of the box — just declare it in CSS. With disableSnapOnDrag (on by default) a free mouse drag temporarily turns it off so it doesn't fight the drag, while the prev/next buttons scroll to an exact item and keep snap on:

.horizontal-scroller {
    scroll-snap-type: x mandatory;
}
.item {
    scroll-snap-align: start;
}

Optional: a thin scrollbar

A hairline scrollbar drawn inside a taller, easier-to-grab track, using WebKit's ::-webkit-scrollbar pseudo-elements. The gradients paint a 1px line for the track and a slightly thicker line for the thumb (swap #1f7a4d for your accent colour):

.horizontal-scroller::-webkit-scrollbar {
    height: 13px;
}
.horizontal-scroller::-webkit-scrollbar-track {
    background: linear-gradient(transparent, transparent 6px, #1f7a4d 6px, #1f7a4d 7px, transparent 7px);
}
.horizontal-scroller::-webkit-scrollbar-thumb {
    background: linear-gradient(transparent, transparent 2px, #1f7a4d 2px, #1f7a4d 11px, transparent 11px);
}
.horizontal-scroller::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(transparent, transparent 2px, #000 2px, #000 11px, transparent 11px);
}

Note: WebKit (Chrome/Safari) only. Do not also set the standard scrollbar-width or scrollbar-color — Chrome ignores every ::-webkit-scrollbar-* rule the moment either is present, and you'd lose the hairline. Firefox falls back to its default scrollbar.

Dragging

While dragging, the element gets a dragging class (e.g. to switch the cursor to grabbing). See demo.html for a full working demo.