Vant3+ts dropdownmenu drop-down menu, multi data can be scrolled

The business need is this effect

The cause of this incident is js Code

let flag = ref(true)
function scrolling(e: any) {
    let scrollBottom =
        e.target.scrollHeight -
        e.target.scrollTop -
        e.target.clientHeight;
    if (scrollBottom < 40) {  // This is to prevent the list from loading all the time 
        if (flag.value) {
            getCenter()
            flag.value = false
            setTimeout(() => {
                flag.value = true

            }, 1000);
        }
    }
}
// When opening the drop-down box 
function open() {
    nextTick(() => {
        let element = document.getElementById('aaa')
        if (element) {
            element.addEventListener('scroll', scrolling)

        }

    })
}
// Obtain transfer center 
function getCenter() {
    menuLoading.value = true
    let param = {
        code: userInfo.staffNo,
        current: menuData.current,
        size: menuData.size
    }
    AjaxGetOrder.selectCenter(param).then(res => {
        const { records, total } = res.data
        menuData.total = total
        status.runStatusList = menuData.current == 1 ? records : status.runStatusList.concat(records || [])
        if (records.length == 0) {
            return
        }
        if (menuData.total > status.runStatusList.length) {
            menuData.current += 1
        } else {
            return

        }
    })
}