@jill64/svelte-dark-theme

Device
'light'

$setting
'sync'

$theme
'light'

<!-- +layout.svelte -->
<script>
  import { ThemeManager } from '@jill64/svelte-dark-theme'
</script>

<ThemeManager />

<script>
  import { theme } from '@jill64/svelte-dark-theme'

  // current theme is 'light'
  console.log($theme)

  // current setting is 'sync'
  console.log($setting)

  const change_to_dark = () => {
    $theme = 'dark'
  }
</script>

// hooks.server.js
import { onRender } from '@jill64/svelte-dark-theme'
export const handle = onRender()