The read-only CSSKeyframeRule.style property is the CSSStyleDeclaration interface for the declaration block of the CSSKeyframeRule.

A CSSStyleDeclaration object, with the following properties:

computed flag

Unset.

declarations

The declared declarations in the rule, in the order they were specified, shorthand properties expanded to longhands.

parent CSS rule

The context object, which is an alias for this.

owner node

Null.

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, which will contain individual CSSKeyFrameRule objects for each keyframe.

@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[0].style); // a CSSStyleDeclaration