Accessible dropdown menu

<nav class="menubar" aria-label="Main">
  <a class="item" href="/">Home</a>

  <div class="hasmenu">
    <button class="item" aria-expanded="false" aria-controls="m-products">
      Products
      <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M6 9l6 6 6-6"/></svg>
    </button>
    <div class="panel" id="m-products">
      <a href="/shirts/"><strong>Shirts</strong><span>Linen, oxford and flannel</span></a>
      <a href="/knitwear/"><strong>Knitwear</strong><span>Lambswool and merino</span></a>
      <a href="/accessories/"><strong>Accessories</strong><span>Scarves, belts and bags</span></a>
    </div>
  </div>

  <div class="hasmenu">
    <button class="item" aria-expanded="false" aria-controls="m-about">
      About
      <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M6 9l6 6 6-6"/></svg>
    </button>
    <div class="panel" id="m-about">
      <a href="/studio/"><strong>The studio</strong><span>Where things are made</span></a>
      <a href="/people/"><strong>People</strong><span>Who makes them</span></a>
    </div>
  </div>

  <a class="item" href="/contact/">Contact</a>
</nav>

* { box-sizing: border-box; margin: 0; }
body { font: 16px/1.6 system-ui, -apple-system, sans-serif; padding: 20px; }

.menubar {
  display: flex;
  gap: 2px;
  padding: 6px;
  border: 1px solid #e2e7ef;
  border-radius: 10px;
  background: #fff;
  width: max-content;
}

.item {
  font: inherit;
  font-size: .94rem;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 14px;
  border: 0;
  border-radius: 7px;
  background: none;
  color: #5b6b83;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
}

.item:hover { background: #f2f5f9; color: #16202e; }
.item:focus-visible { outline: 2px solid #3b4fe4; outline-offset: 2px; }

.item svg {
  width: 13px;
  height: 13px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  transition: transform .16s ease;
}

.item[aria-expanded="true"] { background: #eef0fe; color: #2a3abf; }
.item[aria-expanded="true"] svg { transform: rotate(180deg); }

.hasmenu { position: relative; }

.panel {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  min-width: 260px;
  padding: 6px;
  background: #fff;
  border: 1px solid #e2e7ef;
  border-radius: 10px;
  box-shadow: 0 2px 4px rgba(22,32,46,.04), 0 14px 34px -18px rgba(22,32,46,.4);
  display: none;
  z-index: 20;
}

/* hover for mouse, aria-expanded for keyboard and touch */
.hasmenu:hover > .panel,
.item[aria-expanded="true"] + .panel { display: block; }

.panel a {
  display: block;
  padding: 9px 12px;
  border-radius: 6px;
  text-decoration: none;
  color: #16202e;
}

.panel a:hover { background: #f2f5f9; }
.panel a strong { display: block; font-weight: 500; font-size: .92rem; }
.panel a span { display: block; font-size: .81rem; color: #8593ab; margin-top: 1px; }

@media (hover: none) {
  /* on touch, hover would open and never close */
  .hasmenu:hover > .panel { display: none; }
  .item[aria-expanded="true"] + .panel { display: block; }
}

const buttons = [...document.querySelectorAll(".hasmenu > .item")];

function closeAll(except) {
  buttons.forEach((b) => {
    if (b !== except) b.setAttribute("aria-expanded", "false");
  });
}

buttons.forEach((btn) => {
  btn.addEventListener("click", (e) => {
    e.stopPropagation();
    const open = btn.getAttribute("aria-expanded") === "true";
    closeAll(btn);
    btn.setAttribute("aria-expanded", open ? "false" : "true");
  });
});

document.addEventListener("click", () => closeAll(null));

document.addEventListener("keydown", (e) => {
  if (e.key !== "Escape") return;
  const open = buttons.find((b) => b.getAttribute("aria-expanded") === "true");
  if (open) {
    open.setAttribute("aria-expanded", "false");
    open.focus();
  }
});

// arrow keys walk the open panel
document.querySelector(".menubar").addEventListener("keydown", (e) => {
  if (e.key !== "ArrowDown" && e.key !== "ArrowUp") return;
  const group = e.target.closest(".hasmenu");
  if (!group) return;

  const btn = group.querySelector(".item");
  const links = [...group.querySelectorAll(".panel a")];
  if (!links.length) return;

  if (e.target === btn) {
    e.preventDefault();
    btn.setAttribute("aria-expanded", "true");
    links[e.key === "ArrowDown" ? 0 : links.length - 1].focus();
    return;
  }

  const i = links.indexOf(e.target);
  if (i === -1) return;
  e.preventDefault();
  const next = e.key === "ArrowDown" ? i + 1 : i - 1;
  if (next < 0) btn.focus();
  else if (next < links.length) links[next].focus();
});