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 September 2015.

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

Specifications

Specification
CSS Animations Level 1 # interface-csskeyframesrule-appendrule

Browser compatibility

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