If you are looking to exclusively focus on the prefers-color-scheme aspect, you have the option to customize Bootstrap with Sass and define the variable $color-mode-type: media-query;
In case the user needs the ability to switch between light and dark modes and have their choice saved, utilizing localStorage along with data attributes is recommended (as demonstrated in the question). The library does not have a built-in solution for this. The Bootstrap documentation includes a code snippet for implementation:
/*!
* Color mode toggler for Bootstrap's docs (https://getbootstrap.com/)
* Copyright 2011-2023 The Bootstrap Authors
* Licensed under the Creative Commons Attribution 3.0 Unported License.
*/
(() => {
'use strict'
const getStoredTheme = () => localStorage.getItem('theme')
const setStoredTheme = theme => localStorage.setItem('theme', theme)
const getPreferredTheme = () => {
const storedTheme = getStoredTheme()
if (storedTheme) {
return storedTheme
}
return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
}
const setTheme = theme => {
if (theme === 'auto' && window.matchMedia('(prefers-color-scheme: dark)').matches) {
document.documentElement.setAttribute('data-bs-theme', 'dark')
} else {
document.documentElement.setAttribute('data-bs-theme', theme)
}
}
setTheme(getPreferredTheme())
const showActiveTheme = (theme, focus = false) => {
const themeSwitcher = document.querySelector('#bd-theme')
if (!themeSwitcher) {
return
}
const themeSwitcherText = document.querySelector('#bd-theme-text')
const activeThemeIcon = document.querySelector('.theme-icon-active use')
const btnToActive = document.querySelector(`[data-bs-theme-value="${theme}"]`)
const svgOfActiveBtn = btnToActive.querySelector('svg use').getAttribute('href')
document.querySelectorAll('[data-bs-theme-value]').forEach(element => {
element.classList.remove('active')
element.setAttribute('aria-pressed', 'false')
})
btnToActive.classList.add('active')
btnToActive.setAttribute('aria-pressed', 'true')
activeThemeIcon.setAttribute('href', svgOfActiveBtn)
const themeSwitcherLabel = `${themeSwitcherText.textContent} (${btnToActive.dataset.bsThemeValue})`
themeSwitcher.setAttribute('aria-label', themeSwitcherLabel)
if (focus) {
themeSwitcher.focus()
}
}
window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', () => {
const storedTheme = getStoredTheme()
if (storedTheme !== 'light' && storedTheme !== 'dark') {
setTheme(getPreferredTheme())
}
})
window.addEventListener('DOMContentLoaded', () => {
showActiveTheme(getPreferredTheme())
document.querySelectorAll('[data-bs-theme-value]')
.forEach(toggle => {
toggle.addEventListener('click', () => {
const theme = toggle.getAttribute('data-bs-theme-value')
setStoredTheme(theme)
setTheme(theme)
showActiveTheme(theme, true)
})
})
})
})()