Alternancia automática y manual del modo oscuro

El objetivo

Descripción general de la arquitectura

Configuración de tokens CSS

<div class="demo" data-theme="dark">Dark token demo</div>
<div class="demo" data-theme="light">Light token demo</div>

Lógica de alternancia en JavaScript

<div class="demo" id="theme-demo">Toggle my theme</div>
<div class="demo" data-theme="dark">Dark override example</div>
<button id="toggle-btn">Toggle Theme</button>
<script>
  function toggleTheme() {
    const current = document.getElementById('theme-demo').dataset.theme;
    const system = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
    if (!current) {
      const next = system === 'dark' ? 'light' : 'dark';
      document.getElementById('theme-demo').dataset.theme = next;
    } else {
      delete document.getElementById('theme-demo').dataset.theme;
    }
  }
  document.getElementById('toggle-btn').addEventListener('click', toggleTheme);
</script>

Alternancia de tres estados

<div class="demo" id="theme-demo">Cycles: light → system → dark</div>
<div class="demo" data-theme="dark">Dark state example</div>
<p id="state-label">system</p>
<button id="cycle-btn">Cycle Theme</button>
<script>
  const states = ['light', 'system', 'dark'];
  let current = 'system';
  const demo = document.getElementById('theme-demo');
  const label = document.getElementById('state-label');
  document.getElementById('cycle-btn').addEventListener('click', () => {
    current = states[(states.indexOf(current) + 1) % states.length];
    label.textContent = current;
    if (current === 'system') { delete demo.dataset.theme; } else { demo.dataset.theme = current; }
  });
</script>

Cómo evitar el parpadeo del tema incorrecto

<pre class="code-sample">&lt;!-- In &lt;head&gt;, before any styles --&gt;
&lt;script&gt;
  const t = localStorage.getItem("theme");
  if (t) document.documentElement.dataset.theme = t;
&lt;/script&gt;</pre>

Accesibilidad del botón de alternancia

<button id="theme-toggle" aria-label="Switch to dark mode">🌙</button>

Transición de tema animada

<div class="demo" id="at-demo">Smooth theme transition</div>
<button onclick="document.documentElement.classList.add('theme-transitioning'); const d=document.getElementById('at-demo'); const dark = d.style.background==='rgb(17, 17, 17)'; d.style.background = dark ? '#fff' : '#111'; d.style.color = dark ? '#111' : '#fff'; setTimeout(()=>document.documentElement.classList.remove('theme-transitioning'),250);">Toggle</button>

Escucha de cambios del sistema

<p id="status">Listening for system theme changes…</p>
<script>
  window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', (e) => {
    document.getElementById('status').textContent = 'System changed to ' + (e.matches ? 'dark' : 'light');
  });
</script>

Iconos del modo oscuro

<div>Light: <span class="icon-sun">☀️</span><span class="icon-moon">🌙</span></div>
<div data-theme="dark">Dark: <span class="icon-sun">☀️</span><span class="icon-moon">🌙</span></div>

Resumen: lista de comprobación de implementación

Comprobación rápida

Resumen