js 显示模态框

<!-- 按钮触发模态框 -->
<button id="openModalBtn">打开模态框</button>

<!-- 模态框结构 -->
<div id="myModal" class="modal">
  <div class="modal-content">
    <span class="close">&times;</span>
    <p>这是一个模态框！</p>
  </div>
</div>

/* 模态框背景样式 */
.modal {
  display: none; 
  position: fixed; 
  z-index: 1; 
  left: 0;
  top: 0;
  width: 100%; 
  height: 100%;
  overflow: auto; 
  background-color: rgba(0,0,0,0.4); 
}

/* 模态框内容样式 */
.modal-content {
  background-color: #fefefe;
  margin: 15% auto; 
  padding: 20px;
  border: 1px solid #888;
  width: 80%; 
}

/* 关闭按钮样式 */
.close {
  color: #aaa;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

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

// 获取元素
var modal = document.getElementById("myModal");
var btn = document.getElementById("openModalBtn");
var span = document.getElementsByClassName("close")[0];

// 点击按钮打开模态框
btn.onclick = function() {
  modal.style.display = "block";
}

// 点击关闭按钮关闭模态框
span.onclick = function() {
  modal.style.display = "none";
}

// 点击模态框外部区域关闭模态框
window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}