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Astro

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Adding dark mode to your astro app.

Dark mode

Create an inline theme script

src/pages/index.astro
---
import '../styles/globals.css'
---

<script is:inline>
    const getThemePreference = () => {
        if (typeof localStorage !== 'undefined' && localStorage.getItem('theme')) {
            return localStorage.getItem('theme');
        }
        return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
    };
    const isDark = getThemePreference() === 'dark';
    document.documentElement.classList[isDark ? 'add' : 'remove']('dark');

    if (typeof localStorage !== 'undefined') {
        const observer = new MutationObserver(() => {
            const isDark = document.documentElement.classList.contains('dark');
            localStorage.setItem('theme', isDark ? 'dark' : 'light');
        });
        observer.observe(document.documentElement, { attributes: true, attributeFilter: ['class'] });
    }
</script>

<html lang="en">
    <body>
      <h1>Astro</h1>
    </body>
</html>
</script>

Install Dependencies

pnpm add @vueuse/core

Optional, to include icons for theme button.

pnpm add -D @iconify/vue @iconify-json/radix-icons

Add a mode toggle

Place a mode toggle on your site to toggle between light and dark mode.

We're using useColorMode from @vueuse/core.

Reactive color mode (dark / light / customs) with auto data persistence.

components/ModeToggle.vue
<script setup lang="ts">
import { Icon } from '@iconify/vue'
import { useColorMode } from '@vueuse/core'
import { Button } from '@/components/ui/button'
import { DropdownMenu, DropdownMenuContent, DropdownMenuItem, DropdownMenuTrigger } from '@/components/ui/dropdown-menu'

const mode = useColorMode()
</script>

<template>
  <DropdownMenu>
    <DropdownMenuTrigger as-child>
      <Button variant="outline">
        <Icon icon="radix-icons:moon" class="h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
        <Icon icon="radix-icons:sun" class="absolute h-[1.2rem] w-[1.2rem] rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100" />
        <span class="sr-only">Toggle theme</span>
      </Button>
    </DropdownMenuTrigger>
    <DropdownMenuContent align="end">
      <DropdownMenuItem @click="mode = 'light'">
        Light
      </DropdownMenuItem>
      <DropdownMenuItem @click="mode = 'dark'">
        Dark
      </DropdownMenuItem>
      <DropdownMenuItem @click="mode = 'auto'">
        System
      </DropdownMenuItem>
    </DropdownMenuContent>
  </DropdownMenu>
</template>

Display the mode toggle

Place a mode toggle on your site to toggle between light and dark mode.

src/pages/index.astro
---
import '../styles/globals.css'
import ModeToggle from '@/components/ModeToggle.vue';
---

<!-- Inline script -->

<html lang="en">
    <body>
      <h1>Astro</h1>
      <ModeToggle client:load />
    </body>
</html>
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