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Van11y Accessible hide/show (collapsible regions) using ARIA


This script will transform a simple list of Hx/contents into shiny and accessible hide/show – collapsible regions – using ARIA.

The demo is here:

Website is here:

La page existe aussi en français :

How it works

Basically, it transforms this:

<h2 class="js-expandmore">Lorem dolor si amet</h2>
<div class="js-to_expand">
   here the hidden content

Into this:

<h2 class="js-expandmore">
  <button data-controls="expand_1" aria-expanded="false" class="expandmore__button" type="button">Lorem dolor si amet</button>
<div id="expand_1" class="js-to_expand" data-labelledby="label_expand_1" data-hidden="true">
   here the hidden content

Attribute values are generated on-the-fly (data-controls="expand_1", id="expand_1", data-labelledby="label_expand_1"), no need to worry about it.

The script is launched when the page is loaded. If you need to execute it on AJAX-inserted content, you may use for example on <div id="newContent">your expand source</div>:

var my_expand = van11yAccessibleHideShowAria();

How to use it

Download the script

You may use npm command: npm i van11y-accessible-hide-show-aria. You may also use bower: bower install van11y-accessible-hide-show-aria.


Please follow this convention (the conventions may be adapted to your needs, see in bonuses):

<h2 class="js-expandmore">Lorem dolor si amet</h2>
<div class="js-to_expand">
   here the hidden content

For accessibility reasons, you shall add class="js-expandmore" on an Hx (h1, h2, h3, etc.). Elements that have js-expandmore and js-to_expand classes must be adjacent.

Then use the script, it will do the rest.

Styles needed to work

The minimal style needed is:

.js-to_expand[data-hidden=true] {
  display: none;

However, as the plugin adds a button into a Hx, you will have to style this case. Here is an example:

.expandmore__button {
  background: none;
  font-size: inherit;
  color: inherit;
/* optional */
.expandmore__button:before {
  content : '+ ';
.expandmore__button[data-expanded=true]:before {
  content : '- ';

How to create different styles?

It is possible and very simple, you may use the attribute data-hideshow-prefix-class="<your_value>" like this:

<h2 class="js-expandmore" data-hideshow-prefix-class="mini-combo">Lorem dolor si amet</h2>
<div class="js-to_expand">
   here the hidden content

It will prefix generated classes, <your_value>-expandmore__button and <your_value>-expandmore__to_expand, like this:

<h2 class="js-expandmore" data-hideshow-prefix-class="mini-combo">
 <button id="label_expand_2" class="mini-combo-expandmore__button js-expandmore-button" data-controls="expand_2" aria-expanded="false" type="button">
  Lorem dolor si amet
<div id="expand_2" class="js-to_expand mini-combo-expandmore__to_expand" data-hidden="true" data-labelledby="label_expand_2">
 here the hidden content

The script will prefix all classes, so you will able to style elements as you want. If you don’t use it, the script won’t mind.


Opened by default

No problem, it is possible and very simple, use the class is-opened on:

<h2 class="js-expandmore">Lorem dolor si amet</h2>
<div class="js-to_expand is-opened">
   here the hidden content

The script will detect it, and make it open by default. As simple as one copy/paste.


No problem, it is possible using some CSS transitions. You have to keep in mind several things to keep it accessible:

  • You can’t animate the display property, and height property might be complicated too to animate.
  • So you can’t use display: none; to hide a content (even for assistive technologies).
  • You have to set up visibility to visible or hidden to show/hide a content.
  • Basically, you should animate max-height, opacity (if needed), and use visibility to hide content to assistive technology.

If you have clicked on this section, you might have noticed the animation. Let’s assume we are using this source:

<h2 class="js-expandmore mb0 mt0" data-hideshow-prefix-class="animated">Bonus: some animations?</h2>
 <div class="js-to_expand"></div>

So here is the CSS code (unprefixed):

/* This is the opened state */
.animated-expandmore__to_expand {
 display: block;
 overflow: hidden;
 opacity: 1;
 transition: visibility 0s ease, max-height 2s ease, opacity 2s ease ;
 max-height: 80em;
 /* magic number for max-height = enough height */
 visibility: visible;
 transition-delay: 0s;
/* This is the hidden state */
[data-hidden=true].animated-expandmore__to_expand {
 display: block;
 max-height: 0;
 opacity: 0;
 visibility: hidden;
 transition-delay: 2s, 0s, 0s;

Here is the trick: from “hidden” to “visible” state, visibility is immediately set up to visible, and max-height/opacity are “normally” animated.

From “visible” to “hidden” state, the visibility animation is delayed. So the content will be immediately hidden… at the end of the animation of max-height/opacity.

Default config

const CONFIG = {
    HIDESHOW_EXPAND: 'js-expandmore',
    HIDESHOW_BUTTON_EXPAND: 'js-expandmore-button',
    HIDESHOW_BUTTON_EXPAND_STYLE: 'expandmore__button',
    HIDESHOW_BUTTON_LABEL_ID: 'label_expand_',

    DATA_PREFIX_CLASS: 'data-hideshow-prefix-class',


    HIDESHOW_TO_EXPAND_ID: 'expand_',
    HIDESHOW_TO_EXPAND_STYLE: 'expandmore__to_expand',

     recommended settings by a11y expert
    ATTR_CONTROL: 'data-controls',
    ATTR_EXPANDED: 'aria-expanded',
    ATTR_LABELLEDBY: 'data-labelledby',
    ATTR_HIDDEN: 'data-hidden',

    IS_OPENED_CLASS: 'is-opened',

    DISPLAY_FIRST_LOAD: 'js-first_load',

If you need to use another configuration, you may call the plugin like this:

var other_expand = van11yAccessibleHideShowAria({
     HIDESHOW_EXPAND: 'js-expandmore2',
     DATA_PREFIX_CLASS: 'data-hideshow-prefix-class2'

ARIA attributes or data attributes?

No problem. At the beginning of the plugin, you can set up the attributes you need for your special case.

ATTR_CONTROL: 'data-controls',
ATTR_EXPANDED: 'aria-expanded',
ATTR_LABELLEDBY: 'data-labelledby',
ATTR_HIDDEN: 'data-hidden',

However, the default settings are recommended by accessibility experts.

If you need to update, you can do it anyway, the plugin will adapt itself. Example:

var my_expand = van11yAccessibleHideShowAria({
    ATTR_CONTROL: 'aria-controls',
    ATTR_EXPANDED: 'aria-expanded',
    ATTR_LABELLEDBY: 'aria-labelledby',
    ATTR_HIDDEN: 'aria-hidden',

Of course, you will have to update your CSS by using the good attributes.


ES2015 accessible hide-show system (collapsible regions), using ARIA








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