CSS 遷移の完了を検出するにはどうすればよいですか?

const transitionEndEventName = "XXX"; // Determine the appropriate event name
const elemToAnimate = ...; // Element to animate
let done = false;
const transitionEnded = () => {
  done = true;
  // Transition finished actions
  elemToAnimate.removeEventListener(transitionEndEventName, transitionEnded, false);
};
elemToAnimate.addEventListener(transitionEndEventName, transitionEnded, false);

// Trigger animation

setTimeout(() => {
  if (!done) {
    console.log("Timeout required to call transition ended.");
    transitionEnded();
  }
}, XXX); // Replace XXX with animation duration plus a grace period