<button id="bgm-btn" onclick="menuswitch()">
      <i class="fas fa-bars"></i>
    </button>
    <div id="brg-menu" class="">
            <i class="fas fa-times"></i>
            <a class="textslide">WHAT WE DO</a>
            <a class="textslide">CASES</a>
            <a class="textslide">WORK</a>
            <a class="textslide">ABOUT</a>
    </div>
    <script>
          function menuswitch() {
            var element = document.getElementById("brg-menu");
            element.classList.add("menu-open");
          }
    </script>