js alert 确定 取消

alert('这是一条消息');

let userConfirmed = confirm('你确定要继续吗？');
if (userConfirmed) {
    // 用户点击了“确定”
} else {
    // 用户点击了“取消”
}

<!-- HTML -->
<div id="myModal" class="modal">
  <div class="modal-content">
    <p>你确定要继续吗？</p>
    <button id="confirmBtn">确定</button>
    <button id="cancelBtn">取消</button>
  </div>
</div>

/* CSS */
.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: 80%;
}

// JavaScript
document.getElementById('confirmBtn').onclick = function() {
    // 用户点击了“确定”
    document.getElementById('myModal').style.display = 'none';
};

document.getElementById('cancelBtn').onclick = function() {
    // 用户点击了“取消”
    document.getElementById('myModal').style.display = 'none';
};

// 显示模态框
document.getElementById('myModal').style.display = 'block';