This pattern shows how to create a switch for your website that allows changing between light and dark themes, and saving that preference for subsequent visits.
Full article · Video on YouTube · Source on Github
<button class="theme-toggle" id="theme-toggle" title="Toggles light & dark" aria-label="auto" aria-live="polite">
<svg class="sun-and-moon" aria-hidden="true" width="24" height="24" viewBox="0 0 24 24">
<mask class="moon" id="moon-mask">
<rect x="0" y="0" width="100%" height="100%" fill="white" />
<circle cx="24" cy="10" r="6" fill="black" />
</mask>
<circle class="sun" cx="12" cy="12" r="6" mask="url(#moon-mask)" fill="currentColor" />
<g class="sun-beams" stroke="currentColor">
<line x1="12" y1="1" x2="12" y2="3" />
<line x1="12" y1="21" x2="12" y2="23" />
<line x1="4.22" y1="4.22" x2="5.64" y2="5.64" />
<line x1="18.36" y1="18.36" x2="19.78" y2="19.78" />
<line x1="1" y1="12" x2="3" y2="12" />
<line x1="21" y1="12" x2="23" y2="12" />
<line x1="4.22" y1="19.78" x2="5.64" y2="18.36" />
<line x1="18.36" y1="5.64" x2="19.78" y2="4.22" />
</g>
</svg>
</button>
@import "https://unpkg.com/open-props/easings.min.css";
.sun-and-moon > :is(.moon, .sun, .sun-beams) {
transform-origin: center;
}
.sun-and-moon > :is(.moon, .sun) {
fill: var(--icon-fill);
}
.theme-toggle:is(:hover, :focus-visible) > .sun-and-moon > :is(.moon, .sun) {
fill: var(--icon-fill-hover);
}
.sun-and-moon > .sun-beams {
stroke: var(--icon-fill);
stroke-width: 2px;
}
.theme-toggle:is(:hover, :focus-visible) .sun-and-moon > .sun-beams {
stroke: var(--icon-fill-hover);
}
[data-theme="dark"] .sun-and-moon > .sun {
transform: scale(1.75);
}
[data-theme="dark"] .sun-and-moon > .sun-beams {
opacity: 0;
}
[data-theme="dark"] .sun-and-moon > .moon > circle {
transform: translateX(-7px);
}
@supports (cx: 1) {
[data-theme="dark"] .sun-and-moon > .moon > circle {
cx: 17;
transform: translateX(0);
}
}
@media (prefers-reduced-motion: no-preference) {
.sun-and-moon > .sun {
transition: transform .5s var(--ease-elastic-3);
}
.sun-and-moon > .sun-beams {
transition: transform .5s var(--ease-elastic-4), opacity .5s var(--ease-3);
}
.sun-and-moon .moon > circle {
transition: transform .25s var(--ease-out-5);
}
@supports (cx: 1) {
.sun-and-moon .moon > circle {
transition: cx .25s var(--ease-out-5);
}
}
[data-theme="dark"] .sun-and-moon > .sun {
transition-timing-function: var(--ease-3);
transition-duration: .25s;
transform: scale(1.75);
}
[data-theme="dark"] .sun-and-moon > .sun-beams {
transition-duration: .15s;
transform: rotateZ(-25deg);
}
[data-theme="dark"] .sun-and-moon > .moon > circle {
transition-duration: .5s;
transition-delay: .25s;
}
}
const storageKey = 'theme-preference'
const onClick = () => {
// flip current value
theme.value = theme.value === 'light'
? 'dark'
: 'light'
setPreference()
}
const getColorPreference = () => {
if (localStorage.getItem(storageKey))
return localStorage.getItem(storageKey)
else
return window.matchMedia('(prefers-color-scheme: dark)').matches
? 'dark'
: 'light'
}
const setPreference = () => {
localStorage.setItem(storageKey, theme.value)
reflectPreference()
}
const reflectPreference = () => {
document.firstElementChild
.setAttribute('data-theme', theme.value)
document
.querySelector('#theme-toggle')
?.setAttribute('aria-label', theme.value)
}
const theme = {
value: getColorPreference(),
}
// set early so no page flashes / CSS is made aware
reflectPreference()
window.onload = () => {
// set on load so screen readers can see latest value on the button
reflectPreference()
// now this script can find and listen for clicks on the control
document
.querySelector('#theme-toggle')
.addEventListener('click', onClick)
}
// sync with system changes
window
.matchMedia('(prefers-color-scheme: dark)')
.addEventListener('change', ({matches:isDark}) => {
theme.value = isDark ? 'dark' : 'light'
setPreference()
})