Robust and accessible

  • As it relies on a basic HTML structure (Hx), even if the JavaScript isn’t loaded, your page will work, it’s another great miracle of progressive enhancement;
  • Keyboard navigation is supported, inspired by ARIA Design Pattern for Hide/Show regions, you can open it using Enter or Space;
  • No inline CSS/JavaScript injected, your DOM stays clean, which is cool for responsive.

It’s (highly) customisable

  • You can style it as you want;
  • You can set up transitions or animations… as you want;
  • You can create namespaces for generated classes if you need different behaviours in the same page;
  • Every aspect of the script can be customized, if you transpile the script into ES5, it will be IE9+ compatible.

Free and no license problem

  • No license problem: it uses MIT license, so it’s free, open-source and you can do whatever you want with it, including commercial use. This permission notice shall be included in all copies or substantial portions of it.
  • However, it is not prohibited to tell me that you’ve used it, or send me a little “thank you”. ;)


  • 6.6kb (development, readable by humans);
  • ~2kb (minified, readable by machines);
  • ~1kb minified and gzipped (readable by… mutants‽‽)

How it is working

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.

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.


Just follow this convention:

<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 plugin, 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 : '- ';

Logic of styling classes

How to create different styles?

It is possible and very simple, just 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, just 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.

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.

const ATTR_CONTROL = 'data-controls';
const ATTR_EXPANDED = 'aria-expanded';
const ATTR_LABELLEDBY = 'data-labelledby';
const 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 do the rest. Of course, you will have to update your CSS by using the good attributes (.js-to_expand[data-hidden=true]).