使用HTML/JS和CSS在单击另一个按钮时打开一列按钮？

<button id="openBtn">打开按钮列</button>
<div id="buttonContainer" style="display: none;">
  <button>按钮1</button>
  <button>按钮2</button>
  <button>按钮3</button>
</div>

var openBtn = document.getElementById("openBtn");
var buttonContainer = document.getElementById("buttonContainer");

openBtn.addEventListener("click", function() {
  buttonContainer.style.display = "block";
});

#buttonContainer {
  display: none;
}