如何在悬停子元素时为父元素设置样式？

问题描述

我知道，不存在 中所示，它实现了技巧多次在树菜单。真的很好。

I know that there does not exist a CSS parent selector, but is it possible to style a parenting element when hovering a child element without such a selector?

To give an example: consider a delete button that when hovered will highlight the element that is about to become deleted:

<div>
    <p>Lorem ipsum ...</p>
    <button>Delete</button>
</div>

By means of pure CSS, how to change the background color of this section when the mouse is over the button?

解决方案

Well, this question is asked many times before, and the short typical answer is: It cannot be done by pure CSS. It's in the name: Cascading Style Sheets only supports styling in cascading direction, not up.

But in most circumstances where this effect is wished, like in the given example, there still is the possibility to use these cascading characteristics to reach the desired effect. Consider this pseudo markup:

<parent>
    <sibling></sibling>
    <child></child>
</parent>

The trick is to give the sibling the same size and position as the parent and to style the sibling instead of the parent. This will look like the parent is styled!

Now, how to style the sibling?

When the child is hovered, the parent is too, but the sibling is not. The same goes for the sibling. This concludes in three possible CSS selector paths for styling the sibling:

parent sibling { }
parent sibling:hover { }
parent:hover sibling { }

These different paths allow for some nice possibilities. For instance, unleashing this trick on the example in the question results in this fiddle:

div {position: relative}
div:hover {background: salmon}
div p:hover {background: white}
div p {padding-bottom: 26px}
div button {position: absolute; bottom: 0}

Obviously, in most cases this trick depends on the use of absolute positioning to give the sibling the same size as the parent, ánd still let the child appear within the parent.

Sometimes it is necessary to use a more qualified selector path in order to select a specific element, as shown in this fiddle which implements the trick multiple times in a tree menu. Quite nice really.

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