Can CSS Selectors Target Elements Based on the State of Other Elements?

How to Select Elements Based on the State of Other Elements with CSS

Introduction

Targeting specific elements has always been a fundamental aspect of CSS. However, complexities arise when we need to style elements based on the state of other elements in the page. This article explores the limitations of current CSS selectors and introduces a potential solution from an upcoming standard.

Limitations of Current CSS Selectors

CSS selectors have several limitations in selecting elements based on the state of others. Firstly, they cannot directly access the state of elements using a parent selector or a previous-sibling selector. Secondly, they can only target a single element as the subject of the selector, preventing us from applying styles to multiple elements based on a condition.

Example: Targeting Elements Based on Hover State

Let's say we have multiple sections on a page. Each section contains a div with a "finished" data attribute representing its status. We want to add a colored border to the blinking and spinning elements in the next section whenever the div with the "finished" attribute is hovered. A straightforward CSS selector for this would be:

section:hover + section .blink,
section:hover + section .spin {
  border: 1px solid red;
}

However, this doesn't work because CSS doesn't have a parent selector to target the div in the first section.

Potential Solution: Selectors 4 and :has()

The upcoming Selectors 4 draft introduces a pseudo-class called :has() which solves this problem. :has() allows us to select elements that have a specific descendant. It takes a relative selector argument that matches descendants of the element on which it is used.

A solution using :has() for the above problem would be:

section:has(div[data-status~=finished]) + section div:matches(.blink, .spin) {
  border: 1px solid red;
}

Here, :has() ensures that the selector only targets sections that contain a div with the "finished" status. It also combines the child combinator with :matches() to target both blinking and spinning elements in the subsequent section.

Conclusion

While current CSS selectors have limitations in selecting elements based on the state of others, the upcoming :has() pseudo-class in Selectors 4 provides a potential solution. It enhances selector syntax, allowing for more flexibility and conditional targeting of elements.

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