js prompt修改样式

<div id="customPrompt" class="modal">
  <div class="modal-content">
    <span class="close-button">&times;</span>
    <p>请输入你的名字:</p>
    <input type="text" id="promptInput" />
    <button id="confirmButton">确定</button>
    <button id="cancelButton">取消</button>
  </div>
</div>

.modal {
  display: none; /* 默认隐藏 */
  position: fixed;
  z-index: 1;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgba(0,0,0,0.4);
}

.modal-content {
  background-color: #fefefe;
  margin: 15% auto;
  padding: 20px;
  border: 1px solid #888;
  width: 300px;
}

.close-button {
  color: #aaa;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

.close-button:hover,
.close-button:focus {
  color: black;
  text-decoration: none;
  cursor: pointer;
}

document.addEventListener('DOMContentLoaded', function() {
  var modal = document.getElementById("customPrompt");
  var btn = document.createElement("button");
  btn.innerHTML = "显示自定义提示";
  btn.onclick = function() {
    modal.style.display = "block";
  }
  document.body.appendChild(btn);

  var span = document.getElementsByClassName("close-button")[0];
  span.onclick = function() {
    modal.style.display = "none";
  }

  window.onclick = function(event) {
    if (event.target == modal) {
      modal.style.display = "none";
    }
  }

  document.getElementById("confirmButton").onclick = function() {
    var userInput = document.getElementById("promptInput").value;
    alert("你输入的名字是: " + userInput);
    modal.style.display = "none";
  }

  document.getElementById("cancelButton").onclick = function() {
    modal.style.display = "none";
  }
});