js的new Date()日期的使用

时间：2023-12-22 15:05:38
<script type="text/javascript">

//js获取某个月的天数

function days(year,month){

    var dayCount;

    now = new Date(year,month, 0);

    dayCount = now.getDate();

    return dayCount;

}

console.log(days(2017,10))

//js计算系统当前日期是星期几的几种方法

console.log(new Date().getDay())

console.log(new Date(2017,7,13).getDay())

//格式化日期：yyyy-MM-dd

function formatDate(date) {

var myyear = date.getFullYear();

var mymonth = date.getMonth()+1;

var myweekday = date.getDate(); 

if(mymonth < 10){

mymonth = "0" + mymonth;

}

if(myweekday < 10){

myweekday = "0" + myweekday;

}

return (myyear+"-"+mymonth + "-" + myweekday);

}

//获取本周第一天的日期

function showWeekFirstDay(){

    var now = new Date(2017,0,1);

    var nowTime = now.getTime() ;

    var day = now.getDay();

    var oneDayTime = 24*60*60*1000 ;

    //显示周一

    if(day == 0){

      day = 7;

    }

    var MondayTime = nowTime - (day-1)*oneDayTime ;

    return formatDate(new Date(MondayTime));

}

console.log(showWeekFirstDay())

//获得本周的结束日期

function getWeekEndDate() {

    var now = new Date(2017,8,5);

    var nowTime = now.getTime() ;

    var day = now.getDay();

    var oneDayTime = 24*60*60*1000 ;

    //显示周一

    if(day == 0){

      day = 7;

    }

    var SundayTime =  nowTime + (7-day)*oneDayTime ;

    return formatDate(new Date(SundayTime));

}

console.log(getWeekEndDate())

//获取本月第一天

function showMonthFirstDay(){

    var Nowdate=new Date(2017,1);

    var MonthFirstDay=new Date(Nowdate.getFullYear(),Nowdate.getMonth(),1);

    M=Number(MonthFirstDay.getMonth())+1

    return MonthFirstDay.getFullYear()+"-"+M+"-"+MonthFirstDay.getDate();

}

console.log(showMonthFirstDay())

//获取本月的最后一天

function showMonthLastDay(){

    var Nowdate=new Date(2017,8);

    var MonthNextFirstDay=new Date(Nowdate.getFullYear(),Nowdate.getMonth()+1,1);

    var MonthLastDay=new Date(MonthNextFirstDay-86400000);

    M=Number(MonthLastDay.getMonth())+1

    return MonthLastDay.getFullYear()+"-"+M+"-"+MonthLastDay.getDate();

}

console.log(showMonthLastDay())

</script>

　　

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