获取本周、本月、本年

let value = 1;
let Nowdate=new Date();
let start='',end='';
if(value == '1'){  //  本周
    let WeekFirstDay=new Date(Nowdate-(Nowdate.getDay()-1)*86400000);  
    let WeekLastDay=new Date((WeekFirstDay/1000+6*86400)*1000); 
    start = WeekFirstDay.getFullYear() + '-' + (WeekFirstDay.getMonth() + 1) + '-' + WeekFirstDay.getDate();
    end = WeekLastDay.getFullYear() + '-' + (WeekLastDay.getMonth() + 1) + '-' + WeekLastDay.getDate();
}else if(value == '2'){  //  本月
    let MonthFirstDay=new Date(Nowdate.getFullYear(),Nowdate.getMonth(),1);  
    let MonthNextFirstDay=new Date(Nowdate.getFullYear(),Nowdate.getMonth()+1,1); 
    let MonthLastDay=new Date(MonthNextFirstDay-86400000); 
    start = MonthFirstDay.getFullYear() + '-' + (MonthFirstDay.getMonth() + 1) + '-' + MonthFirstDay.getDate();
    end = MonthLastDay.getFullYear() + '-' + (MonthLastDay.getMonth() + 1) + '-' + MonthLastDay.getDate();
}else{  //  本年
    let YearFirstDay=new Date(Nowdate.getFullYear(),0);
    let YearLastDay=new Date(Nowdate.getFullYear(),11,31);
    start = YearFirstDay.getFullYear() + '-' + (YearFirstDay.getMonth() + 1) + '-' + YearFirstDay.getDate();
    end = YearLastDay.getFullYear() + '-' + (YearLastDay.getMonth() + 1) + '-' + YearLastDay.getDate();
}