javascript獲取本周、本月、本季度、本年時間

js獲取本周，本月，本季度，本年起止時間，直接上代碼

timeSlotChange(val){
        let startTime, endTime;
        let now = new Date(); //當前日期 
        var nowDayOfWeek = now.getDay(); //今天本周的第幾天
        var nowDay = now.getDate(); //當前日
        let nowMonth = now.getMonth(); //當前月 
        let nowYear = now.getFullYear(); //當前年 
        let jd=Math.ceil((nowMonth + 1) / 3);
        switch (val) {
            case "本周":
            startTime = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek)
            endTime = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek))
            case "本月":
            startTime = new Date(nowYear, nowMonth, 1)
            endTime = new Date(nowYear, nowMonth + 1, 0)
            break;
            case "本季度":
            startTime = new Date(nowYear, (jd-1)*3, 1)
            endTime = new Date(nowYear, jd*3, 0)
            break
            case "本年":
            startTime = new Date(nowYear, 0, 1)
            endTime = new Date(nowYear, 11, 31)
            break
        }
        console.log(startTime,endTime)
      }