使用Flex将四个按钮置于div的中心位置

<div id="button-container"></div>

#button-container {
  display: flex;
  justify-content: center;
  align-items: center;
}

var buttonContainer = document.getElementById("button-container");

for (var i = 1; i <= 4; i++) {
  var button = document.createElement("button");
  button.innerText = "Button " + i;
  buttonContainer.appendChild(button);
}