CSSKeyframesRule.name

The name property of the CSSKeyframeRule interface gets and sets the name of the animation as used by the animation-name property.

A CSSOMString.

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, with the name set to "slidein".

@keyframes slidein {
  from {
    transform: translateX(0%);
  }

  to {
    transform: translateX(100%);
  }
}

let myRules = document.styleSheets[0].cssRules;
let keyframes = myRules[0]; // a CSSKeyframesRule
console.log(keyframes.name); // "slidein"