js根据周几获取本周年月日

/**
     * 根据数字判断获取本周,年月日
     * num 0,1,2,3,4,5,6
     * 周一,周二,周三,周四,周五,周六,周日
     */
    getWeekDate(num) {
        let now = new Date();
        let day = now.getDay(); //今天本周的第几天
        let nowDay = now.getDate(); //当前日 
        let nowMonth = now.getMonth(); //当前月 
        let nowYear = now.getYear(); //当前年 
        let weeks = new Array("1", "2", "3", "4", "5", "6", "7");
        let week = weeks[num];
        day = parseInt(day);
        week = parseInt(week);
        //判断是否是今天
        if (day === week) {
            let yestoday = new Date().getTime();
            now.setTime(yestoday);
            return now.getFullYear() + "-" + now.getMonth() + 1 + "-" + now.getDate();
        }
        //判断是否小于今天
        if (week < day) {
            let weekNum = day - week;
            weekNum = weekNum*86400
            let yestoday = new Date().getTime()-1000*weekNum;
            now.setTime(yestoday);
            return now.getFullYear() + "-" + now.getMonth() + 1 + "-" + now.getDate();
        }
        //判断是否大于今天
        if (week > day) {
            let weekNum = week - day;
            weekNum = weekNum*86400
            let yestoday = new Date().getTime()+1000*weekNum;
            now.setTime(yestoday);
            return now.getFullYear() + "-" + now.getMonth() + 1 + "-" + now.getDate();
        }

        return week;
    }