hexo-theme-butterfly/layout/includes/head/darkmode.pug

if theme.darkmode.enable
  script.
    var activateDarkMode = function () {
      document.documentElement.setAttribute('data-theme', 'dark')
      if (document.querySelector('meta[name="theme-color"]') !== null) {
        document.querySelector('meta[name="theme-color"]').setAttribute('content', '#0d0d0d')
      }
    }
    var activateLightMode = function () {
      document.documentElement.setAttribute('data-theme', 'light')
      if (document.querySelector('meta[name="theme-color"]') !== null) {
        document.querySelector('meta[name="theme-color"]').setAttribute('content', '#ffffff')
      }
    }

    var autoChangeMode = '#{theme.darkmode.autoChangeMode}'
    var t = saveToLocal.get('theme')
    if (autoChangeMode === '1') {
      var isDarkMode = window.matchMedia('(prefers-color-scheme: dark)').matches
      var isLightMode = window.matchMedia('(prefers-color-scheme: light)').matches
      var isNotSpecified = window.matchMedia('(prefers-color-scheme: no-preference)').matches
      var hasNoSupport = !isDarkMode && !isLightMode && !isNotSpecified

      if (t === undefined) {
        if (isLightMode) activateLightMode()
        else if (isDarkMode) activateDarkMode()
        else if (isNotSpecified || hasNoSupport) {
          var now = new Date()
          var hour = now.getHours()
          var isNight = hour <= 6 || hour >= 18
          isNight ? activateDarkMode() : activateLightMode()
        }
        window.matchMedia('(prefers-color-scheme: dark)').addListener(function (e) {
          if (saveToLocal.get('theme') === undefined) {
            e.matches ? activateDarkMode() : activateLightMode()
          }
        })
      } else if (t === 'light') activateLightMode()
      else activateDarkMode()
    } else if (autoChangeMode === '2') {
      now = new Date()
      hour = now.getHours()
      isNight = hour <= 6 || hour >= 18
      if (t === undefined) isNight ? activateDarkMode() : activateLightMode()
      else if (t === 'light') activateLightMode()
      else activateDarkMode()
    } else {
      if (t === 'dark') activateDarkMode()
      else if (t === 'light') activateLightMode()
    }