https://getbootstrap.com/docs/5.3/assets/js/color-modes.js

1/*!
2 * Color mode toggler for Bootstrap's docs (https://getbootstrap.com/)
3 * Copyright 2011-2025 The Bootstrap Authors
4 * Licensed under the Creative Commons Attribution 3.0 Unported License.
5 */
6
7(() => {
8  'use strict'
9
10  const getStoredTheme = () => localStorage.getItem('theme')
11  const setStoredTheme = theme => localStorage.setItem('theme', theme)
12
13  const getPreferredTheme = () => {
14    const storedTheme = getStoredTheme()
15    if (storedTheme) {
16      return storedTheme
17    }
18
19    return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
20  }
21
22  const setTheme = theme => {
23    if (theme === 'auto') {
24      document.documentElement.setAttribute('data-bs-theme', (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'))
25    } else {
26      document.documentElement.setAttribute('data-bs-theme', theme)
27    }
28  }
29
30  setTheme(getPreferredTheme())
31
32  const showActiveTheme = (theme, focus = false) => {
33    const themeSwitcher = document.querySelector('#bd-theme')
34
35    if (!themeSwitcher) {
36      return
37    }
38
39    const themeSwitcherText = document.querySelector('#bd-theme-text')
40    const activeThemeIcon = document.querySelector('.theme-icon-active use')
41    const btnToActive = document.querySelector(`[data-bs-theme-value="${theme}"]`)
42    const svgOfActiveBtn = btnToActive.querySelector('svg use').getAttribute('href')
43
44    document.querySelectorAll('[data-bs-theme-value]').forEach(element => {
45      element.classList.remove('active')
46      element.setAttribute('aria-pressed', 'false')
47    })
48
49    btnToActive.classList.add('active')
50    btnToActive.setAttribute('aria-pressed', 'true')
51    activeThemeIcon.setAttribute('href', svgOfActiveBtn)
52    const themeSwitcherLabel = `${themeSwitcherText.textContent} (${btnToActive.dataset.bsThemeValue})`
53    themeSwitcher.setAttribute('aria-label', themeSwitcherLabel)
54
55    if (focus) {
56      themeSwitcher.focus()
57    }
58  }
59
60  window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', () => {
61    const storedTheme = getStoredTheme()
62    if (storedTheme !== 'light' && storedTheme !== 'dark') {
63      setTheme(getPreferredTheme())
64    }
65  })
66
67  window.addEventListener('DOMContentLoaded', () => {
68    showActiveTheme(getPreferredTheme())
69
70    document.querySelectorAll('[data-bs-theme-value]')
71      .forEach(toggle => {
72        toggle.addEventListener('click', () => {
73          const theme = toggle.getAttribute('data-bs-theme-value')
74          setStoredTheme(theme)
75          setTheme(theme)
76          showActiveTheme(theme, true)
77        })
78      })
79  })
80})()