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makeup-active-descendant

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makeup-active-descendant

Implements ARIA active descendant keyboard navigation.

A vanilla JavaScript port of jquery-active-descendant.

Experimental

This module is still in an experimental state, until it reaches v1.0.0 you must consider all minor releases as breaking changes. Patch releases may introduce new features, but will be backwards compatible.

Install

// via npm
npm install makeup-active-descendant

// via yarn
yarn add makeup-active-descendant

Example 1: Programmatic Relationship

In this example the focusable element is not an ancestor of the "descendant" elements. The module will add aria-owns to create a programmatic relationship between the two elements. This is typical of a combobox or date-picker type pattern.

Starting markup:

<div class="widget">
    <input type="text">
    <ul>
        <li>Item 1</li>
        <li>Item 2</li>
        <li>Item 3</li>
    </ul>
</div>

// require the module
const ActiveDescendant = require('makeup-active-descendant');

// get the widget root element reference
const widgetEl = document.querySelector('.widget');

// get the focus element reference
const focusEl = widgetEl.querySelector('input');

// get the element that contains the "descendant" items.
// This element will be programmatically "owned" by the focus element.
const containerEl = widgetEl.querySelector('ul');

// create an activeDescendant widget instance on the element
const activeDescendant = ActiveDescendant.createLinear(widgetEl, focusEl, containerEl, 'li');

// listen for events (optional)
widgetEl.addEventListener('activeDescendantChange', function(e) {
    console.log(e.detail);
});

Markup after instantiation:

<div class="widget" id="widget-0">
    <input type="text" aria-owns="widget-0-list-0">
    <ul id="widget-0-list-0">
        <li id="widget-0-item-0" data-makeup-index="0">Item 1</li>
        <li id="widget-0-item-1" data-makeup-index="1">Item 2</li>
        <li id="widget-0-item-2" data-makeup-index="2">Item 3</li>
    </ul>
</div>

Markup after pressing down arrow key on focusable element:

<div class="widget" id="widget-0">
    <input type="text" aria-activedescendant="widget-0-item-0" aria-owns="widget-0-list-0">
    <ul id="widget-0-list-0">
        <li class="active-descendant" id="widget-0-item-0" data-makeup-index="0">Item 1</li>
        <li id="widget-0-item-1" data-makeup-index="1">Item 2</li>
        <li id="widget-0-item-2" data-makeup-index="2">Item 3</li>
    </ul>
</div>

Use CSS to style the active descendant however you wish:

.widget .active-descendant {
    font-weight: bold;
}

Example 2: Hierarchy Relationship

In this example the focusable element is an ancestor of the list items and therefore the "descendant" relationship can be automatically determined from the DOM hierarchy. This is typical of a standalone listbox or grid widget.

NOTE: this module does not add any ARIA roles; only states and properties.

Starting markup:

<div class="widget">
    <ul tabindex="0">
        <li>Item 1</li>
        <li>Item 2</li>
        <li>Item 3</li>
    </ul>
</div>

// require the module
const ActiveDescendant = require('makeup-active-descendant');

// get the widget root element reference
const widgetEl = document.querySelector('.widget');

// get the focus element reference
const focusEl = widgetEl.querySelector('ul');

// in this scenario the container element is the same as the focusable element
const containerEl = focusEL;

// create an activeDescendant widget instance on the element
const activeDescendant = ActiveDescendant.createLinear(widgetEl, focusEl, containerEl, 'li');

// listen for events (optional)
widgetEl.addEventListener('activeDescendantChange', function(e) {
    console.log(e.detail);
});

Markup after instantiation:

<div class="widget" id="widget-0">
    <ul id="widget-0-list-0" tabindex="0">
        <li id="widget-0-item-0" data-makeup-index="0">Item 1</li>
        <li id="widget-0-item-1" data-makeup-index="1">Item 2</li>
        <li id="widget-0-item-2" data-makeup-index="2">Item 3</li>
    </ul>
</div>

Markup after pressing down arrow key on focusable element:

<div class="widget" id="widget-0">
    <ul id="widget-0-list-0" aria-activedescendant="widget-0-item-0" tabindex="0">
        <li class="active-descendant" id="widget-0-item-0" data-makeup-index="0">Item 1</li>
        <li id="widget-0-item-1" data-makeup-index="1">Item 2</li>
        <li id="widget-0-item-2" data-makeup-index="2">Item 3</li>
    </ul>
</div>

Use CSS to style the active descendant however you wish:

.widget .active-descendant {
    font-weight: bold;
}

Options

activeDescendantClassName: the HTML class name that will be applied to the ARIA active descendant element (default: 'active-descendant')
autoInit: specify an integer or -1 for initial index (default: 0) (see makeup-navigation-emitter)
autoReset: specify an integer or -1 for index position when focus exits widget (default: null) (see makeup-navigation-emitter)
axis : specify 'x' for left/right arrow keys, 'y' for up/down arrow keys, or 'both' (default: 'both')
useAriaSelected - set to true to use aria-selected state on descendant items (historically required by Safari + Voiceover, but hopefully not needed anymore) (default: false)

Custom Events

activeDescendantChange
- detail
  - fromIndex
  - toIndex

Properties

index: the index position of the current active descendant

Methods

destroy: destroys all event listeners

Dependencies

Polyfills

Development

npm start
npm test
npm run lint
npm run fix
npm run build
npm run clean

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