獲取當前日期是第幾周，以及本周的星期一是幾號

var dateNow = new Date();
var year = dateNow.getFullYear();
var month = dateNow.getMonth() + 1;
var day = dateNow.getDate();
var week = getYearWeek(year, month, day);//今天是第幾周
var WeekFirstDay = new Date(dateNow - (dateNow.getDay() - 1) * 86400000);
var day1 = (WeekFirstDay.getMonth() + 1) + '-' + WeekFirstDay.getDate();//本周星期一的日期
WeekFirstDay.setDate(WeekFirstDay.getDate() + 7);
var day2 = (WeekFirstDay.getMonth() + 1) + '-' + WeekFirstDay.getDate();//下周星期二的日期

function getYearWeek(year, month, date) {
    /*  
        dateNow是當前日期 
        dateFirst是當年第一天  
        dataNumber是當前日期是今年第多少天  
        用dataNumber + 當前年的第一天的周差距的和在除以7就是本年第幾周  
    */
    let dateNow = new Date(year, parseInt(month) - 1, date);
    let dateFirst = new Date(year, 0, 1);
    let dataNumber = Math.round((dateNow.valueOf() - dateFirst.valueOf()) / 86400000);
    return Math.ceil((dataNumber + ((dateFirst.getDay() + 1) - 1)) / 7);
};