let clicking = false;
ul.addEventListener('click', async (event) => {
    const li = event.target.closest('li[data-node-id]');
    if(li.querySelector('.b3-list-item__toggle.fn__hidden')) return;
    if(clicking) return;
    clicking = true;
    setTimeout(() => {
        clicking = false;
    }, 100);
    const arrowBtn = li.querySelector('.b3-list-item__arrow');
    const currentClassList = arrowBtn.classList.toString();
    await whenElementExist(()=>{
        return arrowBtn.classList.toString() !== currentClassList;
    });
    const isOpen = arrowBtn.classList.contains("b3-list-item__arrow--open");
    // 这里判断是否展开  
    console.log(isOpen);
});

​​

‍