是否可以设置仅适用于某个“范围”的 z-index，例如仅影响某个元素的子元素。
我有一个 z-index 为 0 的 containerDiv。它包含一堆圆圈，它们应该以不同的深度相互叠加，但我不希望它们影响页面上的任何其他元素。
我在页面上有一堆其他元素（弹出窗口、下拉菜单等），它们的 z-index 为 1，我希望它们被放置在 containerDiv 及其所有子元素的顶部。由于我很懒，我最好避免必须根据具有最高 z-index 的圆圈来调整这些元素的 z-index 值......如果有某种方式可以让所有其他元素查看 containerDiv，那就太棒了并且所有它的孩子都具有相同的 z-index。
这可以用css实现吗？
The answer depends on whether or not your other elements are descendants of the containerDiv or not. To answer the question: Yes, it's almost certainly possible, given a bit of shuffling of the markup.
But what you need to understand is the concept of stacking context:
http://www.w3.org/TR/CSS2/visuren.html#layers
Stacking context is not inherited the way other properties are: "A stacking context is atomic from the point of view of its parent stacking context; boxes in other stacking contexts may not come between any of its boxes." It's not like every element on the page with z-index:2 will be behind everything on the page with z-index:4. Z-index (combined with a position declaration) is typically (though not exclusively) used to resolve the stacking order when two elements share a containing element.