htz a11y tabs

JavaScript scaffolding for accessible tab interfaces

Installation

jspm install github:haaretz/htz-a11y-tabs

Usage

This module is built to enhance semantic markup into an accessible tab interface, using ARIA and a little javascript.

// Import
import a11yTabs from 'htz-a11y-tabs';

// Instanciate
a11yTabs(tabInterface [,rtl , tablistSelector, tabpanelSelector, activeTab]);

See here for the full JavaScript documentation.

The tablist should be a ul element, with each li containing an anchor element pointing to the relevant tabpanel (which should, in most likelihood be a section or an article element):

<section id="tabInterface">
  <!-- tablist -->
  <ul>
    <li><a href="#section1">Section 1</a></li>
    <li><a href="#section2">Section 2</a></li>
    <li><a href="#section3">Section 3</a></li>
    <li><a href="#section4">Section 4</a></li>
  </ul>

  <!-- tabpanels -->
  <article id="section1">
    <h2>section 1</h2>
  </article>
  <article id="section2">
    <h2>section 2</h2>
  </article>
  <article id="section13">
    <h2>section 3</h2>
  </article>
  <article id="section4">
    <h2>section 4</h2>
  </article>
</section>

The above markup will start us off with a basic list of links to articles within our page, which can still be accessible in the event of any failure in executing the script. Our tab interface can now be progressively enhanced using JavaScript and CSS.

Once our tab interface it initialized, its markup will be transformed into:

<section id="tabInterface">
  <!-- tablist -->
  <ul role="tablist">
    <li role="presentation">
      <a href="#section1" tabindex="0" role="tab" aria-controls="section1" aria-selected="true">Section 1</a>
    </li>
    <li role="presentation">
      <a href="#section2" tabindex="-1" role="tab" aria-controls="section2">Section 2</a>
    </li>
    <li role="presentation">
      <a href="#section3" tabindex="-1" role="tab" aria-controls="section3">Section 3</a>
    </li>
    <li role="presentation">
      <a href="#section4" tabindex="-1" role="tab" aria-controls="section4">Section 4</a>
    </li>
  </ul>

  <!-- tabpanels -->
  <article id="section1" role="tabpanel">
    <h2 tabindex="0">section 1</h2>
  </article>
  <article id="section2" role="tabpanel" aria-hidden="true">
    <h2>section 2</h2>
  </article>
  <article id="section3" role="tabpanel" aria-hidden="true">
    <h2>section 3</h2>
  </article>
  <article id="section4" role="tabpanel" aria-hidden="true">
    <h2>section 4</h2>
  </article>
</section>

Make sure that your css hides tabpanels that have the aria-hidden attribute set to true, and that a tab with the aria-selected attribute set to true are marked as the active tab.

The script enables cycling between the selected tab and its content without having cycle through all the other tabs. As per spec, moving through the tabs is done with left and right arrow keys, while moving between the selected tab and the visible tab panel is done using the tab key.

Pressing the tab key will focus the first element inside the tab panel (which, for semantics sake, should probably be a heading), or the tab panel itself when it does not contain any HTML elements.

Parameters

• container (HTMLElement): The wrapper element around the tabs and tab panels.
• rtl (Boolean): Determine if the tab interface should be right-to-left. Default: false.
• tablistSelector (String): The tablist's selector. Default: 'ul'.
• tabpanelSelector (String): The tabpanels' selector. Default: 'section'.
• activeTab (Integer): The tab number to have initially activated. Zero based. Default: 0.

Events

• 'a11y-tabs:init' - Fired from container after a tab interface has been initialized
• 'a11y-tabs:destroy' - Fired from container after a tab interface has been destroyed
• 'a11y-tabs:before-select' - Fired from container before a tab selection is applied. If the event handler executes event.preventDefault(), the selection will not be applied.
• 'a11y-tabs:after-select' - Fired from container after a tab selection is applied.

See the documentation for details on properties available in each event object.

Instance Methods

Name	Description	Params
isInitialized	Returns true if the instance is initialized	-
visibleTab	Returns the number of the active tab. Zero based	-
init	Initialize an instance	Takes an optional tab number to be made the active tab
destroy	Destroy an instance	Takes an optional boolean, indicating if accessibility attributes should be removed in addition to events. Default: false
goto	Go to a specific tab.	Takes a tab number to go to, and an optional boolean, indicating if focus should be moved inside the tab panel, or remain where is
next	Go to the next tab	Takes an optional boolean, indicating if focus should be moved inside the tab panel, or remain where is
previous	Go to the next tab	Takes an optional boolean, indicating if focus should be moved inside the tab panel, or remain where is