CSSKeyframesRule: appendRule() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨August 2016⁩.

The appendRule() method of the CSSKeyframeRule interface appends a CSSKeyFrameRule to the end of the rules.

Syntax

appendRule(rule)

Parameters

rule: A string containing a keyframe rule.

The CSS includes a keyframes at-rule. This will be the first CSSRule returned by document.styleSheets[0].cssRules. myRules[0] returns a CSSKeyframesRule object. Returning the cssRules property would return a CSSRuleList containing one rule.

After appending another rule with appendRule the cssRules property returns a CSSRuleList containing two rules.

css

@keyframes slide-in {
  from {
    transform: translateX(0%);
  }
}

let myRules = document.styleSheets[0].cssRules;
let keyframes = myRules[0]; // a CSSKeyframesRule
keyframes.appendRule("to {transform: translateX(100%);}");
console.log(keyframes.cssRules); // a CSSRuleList object with two rules