如何在DOM完全呈现时显示按钮

<button id="myButton" style="display: none;">Click Me</button>

document.addEventListener("DOMContentLoaded", function() {
  var button = document.getElementById("myButton");
  button.style.display = "block"; // 或者 button.style.opacity = "1";
});

button {
  transition: opacity 0.5s ease-in-out;
}

button.show {
  opacity: 1;
}

document.addEventListener("DOMContentLoaded", function() {
  var button = document.getElementById("myButton");
  button.classList.add("show");
});