SplitViews

A lightweight, framework-agnostic split-pane library for resizable layouts.
Zero dependencies. Modern Pointer Events. CSS-variable driven sizing.

• ✨ Modern: Uses Pointer Events + setPointerCapture (no global listeners)
• ⚡ Performant: Batched DOM writes, CSS variables for sizes, minimal reflows
• 🧩 Composable: Works with nested splits, no framework required
• ♿ Accessible: ARIA roles, orientations, keyboard focusable gutters

Demo

import SplitViews from "split-views";

Or include it via jsDelivr CDN (UMD):

<script src="https://cdn.jsdelivr.net/npm/split-views/dist/index.umd.min.js"></script>
<!-- Access via global object : window.SplitViews -->

Quick Start

HTML:

<div id="editor" class="split-root" style="height: 400px">
  <div>Left Pane</div>
  <div>Right Pane</div>
</div>

JavaScript:

import SplitViews from "splitviews";

const split = SplitViews({
  root: "#editor",
  direction: "horizontal", // 'vertical' or 'horizontal' (default)
  gutterSize: 8,
  sizes: [30, 70], // percentages; defaults to equal split
  minSize: [120, 200], // px per pane or single px applied to all
  snapOffset: 8, // px tolerance before snapping to min
  onDrag: (sizes) => {
    console.log("resizing...", sizes);
  },
  onDragEnd: (sizes) => {
    console.log("final sizes:", sizes);
  },
});

---

Options

Option	Type	Default	Description
root	HTMLElement | string	required	Container element or selector. Children become panes.
direction	'horizontal' | 'vertical'	'horizontal'	Split direction.
gutterSize	number	10	Gutter thickness in px.
gutterClassName	string	'split-gutter'	Class applied to each gutter.
minSize	number | number[]	0	Per-pane minimum size in px (array) or single px for all.
sizes	number[]	equal split	Initial sizes in percentages.
snapOffset	number	0	Extra px tolerance before snapping to min.
onDrag	(sizes:number[])=>void	—	Called on every drag frame.
onDragEnd	(sizes:number[])=>void	—	Called when dragging stops.

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API

• destroy(): Removes gutters and resets styles
• setSizes(sizes: number[]): Programmatically set pane sizes
• getSizes(): number[]: Get current pane sizes

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Styling

The library sets:

• display: flex and flex-direction on root
• flex-basis per pane (via CSS variables)
• Basic cursor and touch-action on gutters

You control the look of gutters:

.split-root {
  contain: layout size style; /* hint for performance */
}

.split-gutter {
  background: transparent;
  position: relative;
}

/* Visible hairline */
.split-gutter::before {
  content: "";
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.1);
}

.split-gutter:hover::before {
  background: rgba(0, 0, 0, 0.2);
}

CSS variables you can use:

• --pane-<index>-size: applied as flex-basis for each pane
• --split-gutter-size: gutter thickness
• --split-cursor: cursor type (col-resize / row-resize)

---

Accessibility

Gutters automatically have:

• role="separator"
• aria-orientation="vertical" (for horizontal split) or "horizontal" (for vertical split)
• tabIndex="0" so they can be focused

---

Nested Splits

You can nest multiple instances:

const outer = SplitViews({ root: "#root", direction: "horizontal" });
const inner = SplitViews({
  root: '#root [data-split-pane="1"]',
  direction: "vertical",
});

Each instance manages only its direct children.

---

Performance Notes

• Uses setPointerCapture → no global listeners.
• DOM writes batched with requestAnimationFrame.
• CSS variables used for sizes → fast style recalculation.
• Avoid heavy work in onDrag; debounce if needed.
• Clean destroy() ensures no leaks.

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Browser Support

• Chromium, Firefox, Safari (modern versions with Pointer Events).
• No IE support (Pointer Events required).

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License

MIT © 2025