如何在单击按钮时更改背景图像？

<button id="changeBtn">点击更改背景图像</button>
<div id="imageContainer" style="background-image: url('初始背景图像的URL');"></div>

#changeBtn {
  padding: 10px 20px;
  background-color: #ccc;
  border: none;
  cursor: pointer;
}

#imageContainer {
  width: 500px;
  height: 300px;
  background-size: cover;
  background-position: center;
}

var changeBtn = document.getElementById('changeBtn');
var imageContainer = document.getElementById('imageContainer');

changeBtn.addEventListener('click', function() {
  // 在这里更改背景图像的URL
  var newImageUrl = '新的背景图像的URL';
  imageContainer.style.backgroundImage = 'url(' + newImageUrl + ')';
});