AJAX弹出层代码

<div id="popup-container">
  <div id="popup-content">
    <!-- 弹出层的内容 -->
  </div>
</div>
<button onclick="showPopup()">点击打开弹出层</button>

CSS样式：
```css
#popup-container {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 300px;
  height: 200px;
  background-color: #ffffff;
  border: 1px solid #cccccc;
}

#popup-content {
  padding: 20px;
}

JavaScript代码：
```javascript
function showPopup() {
  var popup = document.getElementById("popup-container");
  popup.style.display = "block";
}

function hidePopup() {
  var popup = document.getElementById("popup-container");
  popup.style.display = "none";
}