<div class="menu" tabindex="0">
  <a href="https://google.com" target="_blank" tabindex="-1">Link to Google</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
</div>
<div class="menu" tabindex="0"> 
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
  <a href="#" tabindex="-1">Link</a>
</div>
<p><kbd>Tab</kbd> / <kbd>Shift + Tab</kbd> to switch between the menus, <kbd>🠕</kbd> and <kbd>🠗</kbd> to go up and down inside the menu. <kbd>Space</kbd> to click a link.</p>

* {
  padding: 0;
  margin: 0;
  color: white;
  box-sizing: border-box;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
}

body {
  display: grid;
  grid-auto-flow: column;
  max-width: 40rem;
  margin-inline: auto;
  place-items: center;
  background-color: #111;
  height: 100vh;
}

.menu {
  background-color: ;
  display: flex;
  flex-direction: column;
  border: 1px solid #555;
  border-radius: 0.5rem;
  overflow: hidden;
}

.menu > a {
  padding-inline: 4rem;
  padding-block: 1rem;
}

.menu > * + * {
  border-top: 1px solid #555;
}

.menu:focus-within {
  outline: 0.2rem solid #666;
  outline-offset: 0.25rem;
}

a {
  text-decoration: none;
  text-align: center;
}

a:hover, a:focus {
  background-color: #444850;
  outline: none;
  text-decoration: #aaa underline 0.2rem;
}

kbd {
  padding: 0.5rem;
  margin-inline: 0.2rem;
  border-radius: 0.3rem;
  font-family: monospace;
  border: 0.5px solid #666;
}

p {
  position: absolute;
  left: 2rem;
  top: 2rem;
  line-height: 2.5rem;
}

const menuList = document.querySelectorAll(".menu");

menuList.forEach((menu) => {
  const children = Array.from(menu.children);
  let current = 0;
  const handleKeyDown = (e) => {
    if (!(["ArrowUp", "ArrowDown", "Space"].includes(e.code))) return;
    if(e.code === "Space") {
      children[current].click();
      return;
    }
    const selected = children[current];
    selected.setAttribute("tabindex", -1);
    let next;
    if (e.code === "ArrowDown") {
      next = current + 1;
      if (current == children.length - 1) {
        next = 0;
      }
    } else if ((e.code = "ArrowUp")) {
      next = current - 1;
      if (current == 0) {
        next = children.length - 1;
      }
    }
    children[next].setAttribute("tabindex", 0);
    children[next].focus();
    current = next;
  };

  menu.addEventListener("focus", (e) => {
    if (children.length > 0) {
      menu.setAttribute("tabindex", -1);
      children[current].setAttribute("tabindex", 0);
      children[current].focus();
    }

    menu.addEventListener("keydown", handleKeyDown);
  });

  menu.addEventListener("blur", (e) => {
    menu.removeEventListener("keydown", handleKeyDown);
  });
});