dark-theme.html

<!-- Include Bootstrap 5.3+ and Bootstrap icons -->
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.1/dist/css/bootstrap.min.css" rel="stylesheet">
<link href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.10.5/font/bootstrap-icons.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.1/dist/js/bootstrap.bundle.min.js"></script>

<nav class="navbar navbar-expand-lg bg-body-tertiary">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">Navbar</a>

    <!-- Copy this dropdown anywhere in your page, e.g. inside a navbar -->
    <div class="position-relative" role="group" aria-label="Toggle dark mode" title="Toggle Dark Mode">
      <button class="dark-theme-toggle btn btn-primary dropdown-toggle" type="button" data-bs-toggle="dropdown" aria-expanded="false" aria-label="Open navigation menu">
        <i class="bi bi-circle-half"></i> <span class="d-lg-none ms-2">Toggle theme</span>
      </button>
      <ul class="dropdown-menu dropdown-menu-end">
        <li><button class="dropdown-item" data-bs-theme-value="light"><i class="me-2 bi bi-sun-fill"></i> Light</button></li>
        <li><button class="dropdown-item" data-bs-theme-value="dark"><i class="me-2 bi bi-moon-stars-fill"></i> Dark</button></li>
        <li><button class="dropdown-item" data-bs-theme-value="auto"><i class="me-2 bi bi-circle-half"></i> Auto</button></li>
      </ul>
    </div>

  </div>
</nav>

<!-- This uses the .dark-theme-toggle class and the data-bs-theme-value= attribute to change color theme -->
<script src="../dist/dark-theme.js" type="module"></script>