如果父div内部有4个或更多div，则显示滚动箭头容器

<div class="parent-div">
  <div class="child-div">内容1</div>
  <div class="child-div">内容2</div>
  <div class="child-div">内容3</div>
  <div class="child-div">内容4</div>
  <div class="child-div">内容5</div>
  <div class="child-div">内容6</div>
  <!-- 更多div... -->
</div>

.parent-div {
  width: 100%;
  height: 300px;
  overflow-x: auto;
  white-space: nowrap;
  position: relative;
}

.child-div {
  display: inline-block;
  width: 200px;
  height: 100%;
  /* 其他样式设置 */
}

.parent-div::after {
  content: '';
  width: 20px;
  height: 20px;
  background-image: url('scroll-arrow.png'); /* 滚动箭头的图标 */
  background-size: cover;
  position: absolute;
  top: 50%;
  right: 0;
  transform: translateY(-50%);
  cursor: pointer;
  opacity: 0.5;
  transition: opacity 0.3s ease;
}

.parent-div:hover::after {
  opacity: 1;
}

.parent-div::-webkit-scrollbar {
  width: 8px;
  background-color: #f1f1f1;
}

.parent-div::-webkit-scrollbar-thumb {
  background-color: #888;
  border-radius: 4px;
}

.parent-div::-webkit-scrollbar-thumb:hover {
  background-color: #555;
}