Bootstrap - Toggler not working as it should?

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1

Hello, So I’ve been diving into bootstrap and I’ve tried to create a “toggler” for my site if using mobile devices, I have the code and the toggled shows up but it just doesn’t drop down.

<nav class="navbar navbar-expand-lg bg-danger navbar-dark">
      <button
        class="navbar-toggler"
        type="button"
        data-toggle="collapse"
        data-target="#navbarTogglerDemo01"
        aria-controls="navbarTogglerDemo01"
        aria-expanded="false"
        aria-label="Toggle navigation"
      >
        <span class="navbar-toggler-icon"></span>
      </button>
      
        <a class="navbar-brand">ELectro</a>
        <div class="collapse navbar-collapse" id="navbarTogglerDemo01">
        <ul class="navbar-nav ms-auto">
          <li class="nav-item">
            <a class="nav-link" href=""
              >About</a>
          </li>
          <li class="nav-item">
            <a class="nav-link" href="">Portfolio</a>
          </li>
        </ul>
      </div>
    
    </nav>


  </body>
</html>