How To Construct An Expandable Accessible Gallery

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One of many use circumstances for utilizing CSS Grid is to show a gallery of photos, however a gallery by itself is probably not that thrilling. We may, for instance, add a click on impact to enlarge the picture with out affecting the grid to make it a bit bit extra enjoyable. And naturally, as to not exclude anyone from having fun with this characteristic, we should always make it accessible, too.

On this article, I’ll clarify the way to construct an accessible expandable gallery with a couple of suggestions and tips alongside the best way. Right here’s how the ultimate consequence seems to be like:

See the Pen The right way to construct accessible expandable gallery by Silvestar Bistrović.


First, we’re going to set the HTML construction. After all, we may all the time do it in varied methods, however allow us to use an inventory of photos wrapped in buttons.

<ul class=”js-favs”>
<img src=”/path/to/picture” alt=”” />


Now, to make the gallery accessible, we have to make some changes:

Add the descriptive alt attribute to each picture to assist visually impaired individuals perceive what’s within the picture;
Use the aria-expanded attribute which informs assistive applied sciences if the picture is expanded or not;
Embody function=”checklist” to ensure assistive applied sciences announce the checklist as a result of some display screen readers would possibly take away the checklist announcement.

“It’s not simply utilizing list-style: none, however any CSS that will take away the bullet or quantity indicators of an inventory’s objects will even take away the semantics.”

“Fixing” Lists, Scott O’Hara

Lastly, let’s add a paragraph with useful textual content on the way to use the gallery, and wrap the entire code in a landmark (on this case, the primary aspect).

<p>Use ESC to shut bigger image.</p>
<ul class=”js-favs” function=”checklist”>
<button aria-expanded=”false”>
<img src=”/path/to/picture” alt=”Description of the picture.” />


For the simplicity of the demo, I made a decision to make use of photos wrapped with the aria-expanded attribute. A greater answer could be so as to add solely picture tags after which use JavaScript to wrap these photos in a button with the aria-expanded attribute. This can be thought of as progressive enhancement because the increasing impact wouldn’t work with out JavaScript anyway.


To outline the grid structure, we may use CSS Grid. We’ll use auto-fit in order that objects can match into the out there area, however prohibit themselves from shrinking underneath a sure width. Because of this we’ll see a distinct variety of objects on completely different viewports with out writing too many media queries.

:root {
–gap: 4px;

ul {
show: grid;
grid-template-columns: repeat(1, 1fr);
grid-gap: var(–gap);

@media display screen and (min-width: 640px) {
ul {
grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));

To protect the right facet ratio of the picture, we may use the aspect-ratio property. To reset the button fashion, we may add the all: preliminary declaration. We must also cover the overflow of the button.

To make the picture match proper into the button, we’ll use object-fit: cowl declaration and set each width and top to 100%:

button {
all: preliminary;
show: block;
width: 100%;
aspect-ratio: 2/1;
overflow: hidden;
cursor: pointer;

img {
top: 100%;
width: 100%;
object-fit: cowl;

The increasing impact is completed with the size transformation. The transition is enabled by default, but when the person doesn’t favor transitions and animations, we will use the prefers-reduced-motion media question and set the transition-duration property to 0s.

:root {
–duration-shrink: .5s;
–duration-expand: .25s;
–no-duration: 0s;

li {
transition-property: rework, opacity;
transition-timing-function: ease-in-out;
transition-duration: var(–duration-expand);
} {
transition-duration: var(–duration-shrink);

@media (prefers-reduced-motion) {
li, {
transition-duration: var(–no-duration);

The JavaScript


Earlier than we make the aspect expandable, we have to put together and calculate a couple of issues.

First, we’ll must get the length of the transition by studying the CSS Customized Property –duration-on.

let timeout = 0

// Get the transition timeout from CSS
const getTimeouts = () => {
const durationOn = parseFloat(getComputedStyle(doc.documentElement)

timeout = parseFloat(durationOn) * 1000

Subsequent, we’ll set the info attributes for the later calculation:

the hole of the grid components;
the width of a single aspect;
the variety of objects per row.

The primary two are fairly simple. We may get the values from the computed CSS fashion.

To seek out the variety of columns, we should always iterate by way of every tile and examine the highest place of every aspect. As soon as the highest place modifications, the merchandise is within the new row, which will get us the variety of objects.

// Set knowledge attributes for calculations
const setDataAttrs = ($elems, $mum or dad) => {
// Get the highest offset of the primary aspect
let prime = getTop($elems[0])

// Set grid hole from CSS
const gridColumnGap = parseFloat(getComputedStyle(doc.documentElement)
$mum or dad.setAttribute(‘data-gap’, gridColumnGap)

// Set grid merchandise width from CSS
const eStyle = getComputedStyle($elems[0])
$mum or dad.setAttribute(‘data-width’, eStyle.width)

// Iterate by way of grid objects
for (let i = 0; i < $elems.size; i++) {
const t = getTop($elems[i])

// Test when prime offset modifications
if (t != prime) {
// Set the variety of columns and break cease the loop
$mum or dad.setAttribute(‘data-cols’, i)

Increasing Route

To attain the expandable impact, we should always make some checks and calculations first. First, we should always verify if the merchandise is within the final row and on the finish of the row. If the merchandise is within the final row, it ought to develop to the highest. Meaning it ought to have the transform-origin property set to the underside worth.

Essential: If the aspect ought to develop to 1 path, its transform-origin property needs to be set to an “reverse” worth. Be aware that vertical and horizontal values needs to be mixed.

// Set energetic merchandise
const activateElem = ($elems, $mum or dad, $elem, $button, lengthOfElems, i) => {
// Get knowledge attributes from mum or dad
const cols = parseInt($mum or dad.getAttribute(‘data-cols’))
const width = parseFloat($mum or dad.getAttribute(‘data-width’))
const hole = parseFloat($mum or dad.getAttribute(‘data-gap’))

// Calculate the variety of rows
const rows = Math.ceil(lengthOfElems / cols) – 1

// Calculate if the merchandise is within the final row
const isLastRow = i + 1 > rows * cols
// Set default rework path to prime (develop down)
let transformOrigin = ‘prime’

if (isLastRow) {
// If the merchandise is within the final row, set rework path to backside (develop up)
transformOrigin = ‘backside’

// Calculate if the merchandise is probably the most proper
const isRight = (i + 1) % cols !== 0

if (isRight) {
// If the merchandise is probably the most proper, set rework path to left (develop proper)
transformOrigin += ‘ left’
} else {
// If the merchandise is probably the most proper, set rework path to proper (develop left)
transformOrigin += ‘ proper’

$ = transformOrigin

Increasing Impact

To enlarge the picture with out affecting the grid, we may use CSS transforms. Particularly, we should always use the size transformation. I made a decision to make the picture double in measurement, i.e. the issue is the ratio of the double width of the aspect plus grid-gap.

// Calculate the size coefficient
const scale = (width * 2 + hole) / width

// Set merchandise CSS rework
$ = `scale(${scale})`

Keyboard Assist

Customers who navigate websites through the use of a keyboard ought to be capable of use the gallery. Going by way of the checklist works by default when utilizing key Tab. Emulating the clicking works by default by urgent the Enter key whereas the merchandise is targeted. To boost the default habits, we should always add help for Esc and the arrow keys.

As soon as we develop the merchandise, urgent Esc ought to revert it to its commonplace measurement. We may do it by checking the code of the pressed key. The identical goes for arrow keys, however the motion is completely different. When urgent arrow keys, we wish to get the earlier or subsequent sibling after which emulate the clicking on that aspect.

// Set sibling as an energetic merchandise
const activateSibling = ($sibling) => {
// Discover anchor
const $siblingButton = $sibling.querySelector(‘button’)

// Unset international energetic aspect
$activeElem = false

// Focus and click on on present
$ on()

// Set keyboard occasions
const setKeyboardEvents = () => {
doc.addEventListener(‘keydown’, (e) => {
// Take motion provided that international energetic aspect exists
if ($activeElem) {
// If key’s “escape”, emulate the clicking on the worldwide energetic aspect
if (e.code === ‘Escape’) {
$ on()

// If key’s “left arrow”, activate the earlier sibling
if (e.code === ‘ArrowLeft’) {
const $previousSibling = $activeElem.parentNode.previousElementSibling

if($previousSibling) {

// If key’s “proper arrow”, activate the subsequent sibling
if (e.code === ‘ArrowRight’) {
const $nextSibling = $activeElem.parentNode.nextElementSibling

if($nextSibling) {


To make the gallery aspect expanded, we should always deactivate all different components first. Then, if we click on on the expanded aspect, it ought to revert to the usual measurement.

let $activeElem = false

// Deactivate grid objects
const deactiveElems = ($elems, $mum or dad, $currentElem, $button) => {
// Unset mum or dad class
$mum or dad.classList.take away(‘is-zoomed’)

for (let i = 0; i < $elems.size; i++) {
// Unset merchandise class
$elems[i].classList.take away(‘is-zoomed’)
// Unset merchandise CSS rework
$elems[i].fashion.rework = ‘none’

// Skip the remaining if the merchandise is the present merchandise
if ($elems[i] === $currentElem) {

// Unset merchandise aria expanded if aspect exists
if($button) {
$button.setAttribute(‘aria-expanded’, false)

// Set energetic merchandise
const activateElem = ($elems, $mum or dad, $elem, $button, lengthOfElems, i) => {

// Reset all components
deactiveElems($elems, $mum or dad, $elem, $button)

if ($activeElem) {
$activeElem = false

$activeElem = $button


// Set click on occasions on anchors
const setClicks = ($elems, $mum or dad) => {
$elems.forEach(($elem, i) => {
// Discover anchor
const $button = $elem.querySelector(‘button’)

$button.addEventListener(‘click on’, (e) => {
// Set energetic merchandise on click on
activateElem($elems, $mum or dad, $elem, $button, $elems.size, i)

Z-index Points

To stop points with z-index and stacking context, we should always use the timeout to delay the rework. That’s the similar timeout that we calculated within the preparation part.

// Deactivate grid objects
const deactiveElems = ($elems, $mum or dad, $currentElem, $button) => {
for (let i = 0; i < $elems.size; i++) {

// After a half of the timeout, reset CSS z-index to keep away from overlay points
setTimeout(() => {
$elems[i].fashion.zIndex = 0
}, timeout)

// Set energetic merchandise
const activateElem = ($elems, $mum or dad, $elem, $button, lengthOfElems, i) => {

setTimeout(() => {
// Set mum or dad class
$mum or dad.classList.add(‘is-zoomed’)
// Set merchandise class
// Set merchandise CSS rework
$ = `scale(${scale})`
// Set merchandise aria expanded
$button.setAttribute(‘aria-expanded’, true)
// Set international energetic merchandise
$activeElem = $button
}, timeout)

Viewport Resizing

If the viewport modifications the dimensions, we have to recalculate defaults as a result of we outlined a fluid grid that permits objects to fill the out there area and transfer from row to row.

// Set resize occasions
const setResizeEvents = ($elems, $mum or dad) => {
window.addEventListener(‘resize’, () => {
// Set knowledge attributes for calculations
setDataAttrs($elems, $mum or dad)
// Deactivate grid objects
deactiveElems($elems, $mum or dad)

A Phrase About Accessibility And Credit

I had no issues constructing this demo besides with the accessibility half. I used to be undecided what to do and which aria attributes to make use of at first. Even after determining which attributes to make use of, I couldn’t be 100% certain it was proper. So step one was to take a look at all the pieces with a keyboard. That was the straightforward half. Then I used the VoiceOver utility (since I’m utilizing a Mac) to check the way it works for visually impaired individuals. It sounded adequate to me.

Nonetheless, even in spite of everything that testing, I used to be nonetheless not 100% certain. So I made a decision to ask for assist. I’m part of one Slack neighborhood for designers and builders (BoagWorld), and I posted a query there. Thankfully, accessibility specialists like Todd Libby helped me take a look at the demo on completely different gadgets and proper the code. I additionally requested Manuel Matuzović for assist and he helped me clear up the code.

I’m grateful to have the Web and developer communities the place we will all ask for assist, get solutions from professionals, and resolve issues collectively. That’s very true with delicate points like accessibility. Accessibility is tough, and it doesn’t take a lot to make it improper. Much less is extra — at the least it was in my case.

And eventually, I needed to share the best lesson:

“If you should use a local HTML aspect [HTML51] or attribute with the semantics and habits you require already built-in, as an alternative of re-purposing a component and including an ARIA function, state or property to make it accessible, then accomplish that.”

First Rule of ARIA Use, W3C Working Draft 27 (Sept. 2018)

Additional Studying on Smashing Journal

Accessible SVGs: Inclusiveness Past Patterns, Carie Fisher
A Full Information To Accessible Entrance-Finish Parts, Vitaly Friedman
Creating An Accessible Dialog From Scratch, Kitty Giraudel
When CSS Isn’t Sufficient: JavaScript Necessities For Accessible Parts, Stephanie Eckles
Accessible SVGs: Good Patterns For Display screen Reader Customers, Carie Fisher
How To Construct An Accessible Entrance-Finish Utility With Chakra UI And Nuxt.js, Kelvin Omereshone
Translating Design Wireframes Into Accessible HTML/CSS, Harris Schneiderman

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