Tree

Tree presents nested data as an expandable hierarchy so users can locate, select, and act on nodes one level at a time.

src3 items

components3 items

button.css4 KB

tree.css3 KB

legacy.csslocked

tests1 item

tree.spec.ts

index.ts2 KB

package.json1 KB

InstallTerminal

npm install @a3s-lab/ui@0.4.0

<div class="tree" role="tree" aria-label="Project files">
  <div
    role="treeitem"
    aria-label="src"
    aria-expanded="true"
    aria-selected="false"
    data-value="src"
  >
    <div data-tree-row>
      <svg aria-hidden="true"><!-- folder icon --></svg>
      <span data-tree-label>src</span>
    </div>
    <div role="group">
      <div
        role="treeitem"
        aria-label="tree.js"
        aria-selected="true"
        data-value="src/tree.js"
      >
        <div data-tree-row>
          <svg aria-hidden="true"><!-- file icon --></svg>
          <span data-tree-label>tree.js</span>
        </div>
      </div>
    </div>
  </div>
</div>

import "@a3s-lab/ui/a3s.css";
import "@a3s-lab/ui/all";

Usage

Tree is an A3S application component for file explorers, resource hierarchies, and nested configuration. It is intentionally distinct from Accordion: focus moves between visible nodes, selection is explicit, and branches expose a parent-child hierarchy to assistive technology.

Include CSS

Import Tailwind and one complete A3S UI style bundle.

@import "tailwindcss";
@import "@a3s-lab/ui/a3s.css";

Or import only the base CSS, Tree component CSS, and one style pack.

@import "tailwindcss";
@import "@a3s-lab/ui/base.css";
@import "@a3s-lab/ui/components/tree.css";
@import "@a3s-lab/ui/styles/a3s.css";

Include JavaScript

Load the complete runtime bundle, or load the runtime before the Tree controller.

<script src="/assets/js/runtime.min.js" defer></script>
<script src="/assets/js/tree.min.js" defer></script>

Add the tree HTML

<div class="tree" role="tree" aria-label="Project files">
  <div
    role="treeitem"
    aria-label="src"
    aria-expanded="true"
    aria-selected="false"
    data-value="src"
  >
    <div data-tree-row>
      <svg aria-hidden="true"><!-- folder icon --></svg>
      <span data-tree-label>src</span>
    </div>
    <div role="group">
      <div
        role="treeitem"
        aria-label="tree.js"
        aria-selected="true"
        data-value="src/tree.js"
      >
        <div data-tree-row>
          <svg aria-hidden="true"><!-- file icon --></svg>
          <span data-tree-label>tree.js</span>
        </div>
      </div>
    </div>
  </div>
</div>

Parameters

Markup	Purpose
`.tree[role="tree"]`	Root composite widget. Give it an accessible name with `aria-label` or `aria-labelledby`.
`[role="treeitem"]`	One selectable node. Use `aria-selected`, optional `aria-expanded`, and optional `aria-disabled`.
`[data-tree-row]`	The visual row directly inside a tree item. Clicking an expandable row selects and toggles its branch.
`[role="group"]`	Direct child group owned by an expandable tree item.
`[data-tree-label]`	Primary visible label used for truncation and typeahead fallback.
`[data-tree-meta]`	Optional trailing metadata such as size or item count.
`data-value`	Stable value returned in event details. The item `id` or label is used when omitted.

The controller owns tabindex, synchronizes child-group visibility with aria-expanded, and keeps exactly one enabled visible node in the Tab order.

JavaScript API

const tree = document.querySelector("#project-tree");
const item = tree.querySelector('[data-value="src/components"]');

tree.expand(item, true);
tree.select(item, true);
tree.refresh();

Method	Behavior
`tree.select(item, focus = false)`	Sets the single selected item and optionally moves focus.
`tree.expand(item, expanded = true)`	Opens or closes an item that directly owns a group.
`tree.toggle(item)`	Toggles an expandable item.
`tree.refresh()`	Re-reads dynamically added, removed, or disabled nodes.

Selection emits a bubbling change event with { item, value }. Expansion emits a3s:tree-toggle with { item, value, expanded }.

States and variants

Disabled nodes

Set aria-disabled="true" on a tree item. Disabled nodes remain visible but are skipped by pointer interaction, arrow navigation, and typeahead.

RTL

المصدرعنصران

المكونات

الفهرس

<div
    id="tree-demo-rtl"
    class="tree"
    role="tree"
    aria-label="ملفات المشروع"
    dir="rtl"
  >
    <div
      role="treeitem"
      aria-label="المصدر"
      aria-expanded="true"
      aria-selected="false"
      data-value="src"
    >
      <div data-tree-row>
        <svg
          class="lucide lucide-folder"
          xmlns="http://www.w3.org/2000/svg"
          width="24"
          height="24"
          viewBox="0 0 24 24"
          fill="none"
          stroke="currentColor"
          stroke-width="2"
          stroke-linecap="round"
          stroke-linejoin="round"
        >
          <path d="M2 6a2 2 0 0 1 2-2h5l2 2h9a2 2 0 0 1 2 2v10a2 2 0 0 1-2 2H4a2 2 0 0 1-2-2Z" />
        </svg>
        <span data-tree-label>المصدر</span>
        <span data-tree-meta>عنصران</span>
      </div>
      <div role="group">
        <div
          role="treeitem"
          aria-label="المكونات"
          aria-selected="true"
          data-value="components"
        >
          <div data-tree-row>
            <svg
              class="lucide lucide-folder"
              xmlns="http://www.w3.org/2000/svg"
              width="24"
              height="24"
              viewBox="0 0 24 24"
              fill="none"
              stroke="currentColor"
              stroke-width="2"
              stroke-linecap="round"
              stroke-linejoin="round"
            >
              <path d="M2 6a2 2 0 0 1 2-2h5l2 2h9a2 2 0 0 1 2 2v10a2 2 0 0 1-2 2H4a2 2 0 0 1-2-2Z" />
            </svg>
            <span data-tree-label>المكونات</span>
          </div>
        </div>
        <div
          role="treeitem"
          aria-label="الفهرس"
          aria-selected="false"
          data-value="index"
        >
          <div data-tree-row>
            <svg
              class="lucide lucide-file"
              xmlns="http://www.w3.org/2000/svg"
              width="24"
              height="24"
              viewBox="0 0 24 24"
              fill="none"
              stroke="currentColor"
              stroke-width="2"
              stroke-linecap="round"
              stroke-linejoin="round"
            >
              <path d="M14.5 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V7.5L14.5 2z" />
              <polyline points="14 2 14 8 20 8" />
            </svg>
            <span data-tree-label>الفهرس</span>
          </div>
        </div>
      </div>
    </div>
  </div>

Logical indentation, guide lines, and chevrons follow document direction. In RTL, ArrowLeft expands or enters a branch and ArrowRight collapses or returns to its parent.

Accessibility

Keep tree items as direct children of the root or a direct child role="group".
Give every item a concise accessible name. An explicit aria-label prevents descendant groups or trailing metadata from becoming part of a branch name.
Do not place buttons, links, or form controls inside a tree row. The tree item itself owns focus and selection.
Use Tree for hierarchical choices. Use Accordion for independent disclosure sections and Sidebar for page navigation.

Key	Action
`ArrowDown` / `ArrowUp`	Moves to the next or previous enabled visible node.
`Home` / `End`	Moves to the first or last enabled visible node.
`ArrowRight` / `ArrowLeft`	Expands, enters, collapses, or returns to a parent; directions reverse in RTL.
`Enter` / `Space`	Selects the focused node.
Printable characters	Moves to the next visible node whose label starts with the typed text.

#Tree

#Usage

Include CSS

Include JavaScript

Add the tree HTML

#Parameters

#JavaScript API

#States and variants

#Disabled nodes

#RTL

#Accessibility