KeyframeEffect: target 属性

const emoji = document.querySelector("div"); // element to animate

const rollingKeyframes = new KeyframeEffect(
  emoji,
  [
    { transform: "translateX(0) rotate(0)" }, // keyframe
    { transform: "translateX(200px) rotate(1.3turn)" }, // keyframe
  ],
  {
    // keyframe options
    duration: 2000,
    direction: "alternate",
    easing: "ease-in-out",
    iterations: "Infinity",
  },
);

const rollingAnimation = new Animation(rollingKeyframes, document.timeline);
rollingAnimation.play();

// logs "<div>🤣</div>"
console.log(rollingKeyframes.target);

<div>🤣</div>

body {
  box-shadow: 0 5px 5px pink;
}

div {
  width: fit-content;
  margin-left: calc(50% - 132px);
  font-size: 64px;
  user-select: none;
  margin-top: 1rem;
}