CSSRuleList

A CSSRuleList represents an ordered collection of read-only CSSRule objects.

While the CSSRuleList object is read-only, and cannot be directly modified, it is considered a live object, as the content can change over time.

To edit the underlying rules returned by CSSRule objects, use CSSStyleSheet.insertRule() and CSSStyleSheet.deleteRule(), which are methods of CSSStyleSheet.

The interface has no constructor. An instance of CSSRuleList is returned by CSSStyleSheet.cssRules and CSSKeyframesRule.cssRules.

Note: This interface was an attempt to create an unmodifiable list and only continues to be supported to not break code that's already using it. Modern APIs use types that wrap around ECMAScript array types instead, so you can treat them like ECMAScript arrays, and at the same time impose additional semantics on their usage (such as making their items read-only).

Instance properties

CSSRuleList.length Read only

Returns an integer representing the number of CSSRule objects in the collection.

Instance methods

CSSRuleList.item()

Gets a single CSSRule.

Examples

In the following example there is a stylesheet with three rules. Using CSSStyleSheet.cssRules returns a CSSRuleList, which is printed to the console.

The number of rules in the list is printed to the console using CSSRuleList.length. The first CSSRule can be returned by using 0 as the parameter for CSSRuleList.item, in the example this will return the rules set for the body selector.

CSS

css

body {
  font-family: system-ui, -apple-system, sans-serif;
  margin: 2em;
}

.container {
  display: grid;
  grid-template-columns: repeat(auto-fill, 200px);
}

.container > * {
  background-color: #3740ff;
  color: #fff;
}

JavaScript

js

let myRules = document.styleSheets[0].cssRules;
console.log(myRules);
console.log(myRules.length);
console.log(myRules[0]);

Specifications

Specification
CSS Object Model (CSSOM)
# the-cssrulelist-interface

Browser compatibility

BCD tables only load in the browser

See also