transitionrun

该事件在第一次创建 CSS 过渡 transitionrun 时触发，即在任何开始之前。transition-delay

Examples

这段代码为 transitionrun 事件添加了一个监听器：

el.addEventListener("transitionrun", () => {
  console.log(
    "Transition is running but hasn't necessarily started transitioning yet"
  );
});