如何在我一按下按钮就开始加载活动指示器？

<button id="myButton">开始加载</button>

var button = document.getElementById("myButton");
button.addEventListener("click", startLoading);

function startLoading() {
  var loader = document.createElement("div");
  loader.id = "loader";
  document.body.appendChild(loader);
}

#loader {
  border: 16px solid #f3f3f3;
  border-top: 16px solid #3498db;
  border-radius: 50%;
  width: 120px;
  height: 120px;
  animation: spin 2s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

function startLoading() {
  var loader = document.createElement("div");
  loader.id = "loader";
  loader.textContent = "加载中...";
  document.body.appendChild(loader);
}