js计算前一天和后一天,根据日期计算年月日

function initDate() {
    let _now = new Date();
    const startDate = new Date(`${_now.getFullYear()}/${_now.getMonth() + 1}/${_now.getDate()}`),
        endDate = new Date(`${_now.getFullYear()}/${_now.getMonth() + 1}/${_now.getDate()}`);
    startDate.setDate(endDate.getDate() -1); //前一天
    endDate.setDate(endDate.getDate() + 1); //后一天
};

根据给定日期计算年月日
function  CreateDate(date){
 const weekKey = ['日', '一', '二', '三', '四', '五', '六'];
    const model = {
        date,
        day:date.getDate(),
        month:date.getMonth() + 1,
        year: date.getFullYear(),
        weekday: date.getDay(),
        weekName: weekKey[date.getDay()],
    };
}