在不重新加载的情况下单击按钮时更新模态值

<button onclick="updateModalValue()">点击按钮</button>

function updateModalValue() {
  // 获取模态框元素
  var modal = document.getElementById("myModal");
  
  // 更新模态值
  modal.innerHTML = "新的模态值";
  
  // 显示模态框
  modal.style.display = "block";
}

<div id="myModal" class="modal">
  <div class="modal-content">
    <span class="close">&times;</span>
    <p>模态值</p>
  </div>
</div>

.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);
}

.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;
}