js的弹窗效果

<div id="myModal" class="modal">
  <div class="modal-content">
    <span class="close">&times;</span>
    <p>这是一个自定义弹窗！</p>
  </div>
</div>

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

.modal-content {
  background-color: #fefefe;
  margin: 15% auto; 
  padding: 20px;
  border: 1px solid #888;
  width: 80%; 
}

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

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

// 获取模态弹窗元素
var modal = document.getElementById("myModal");

// 获取关闭按钮元素
var span = document.getElementsByClassName("close")[0];

// 点击按钮打开弹窗
document.getElementById("openModalBtn").onclick = function() {
  modal.style.display = "block";
}

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

// 点击弹窗外部区域关闭弹窗
window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}