我正在設置簽入和簽出日期的開始日期和結束日期的狀態。我得到 validDateRange 它是有效日期和長度的數組。嘗試將總狀態設置為數組長度乘以房間價格，但不知何故反應不更新我的總狀態。TotalCost 的日志完全正確const RoomDetails = (props) => {    const roomDetails = props.location.state;    const [startDate, setStartDate] = useState();    const [startEnd, setEndDate] = useState();    const [total, setTotal] = useState();    const handleOnSelectCalendar = (startDate, endDate, validDateRange) => {        // console.log(startDate, endDate, validDateRange.length);        setStartDate(startDate);        setEndDate(endDate);        // console.log(roomDetails.price, validDateRange.length);        // var totalCost = roomDetails.price * validDateRange.length;        setTotal(roomDetails.price * validDateRange.length);        console.log(startDate, endDate, total); // output: 2020-12-08 2020-12-11 undefined    };    return (...);}