js日期计算及快速获取周、月、季度起止日,获取指定日期周数以及星期几的小例子

functiongetNowFormatDate(theDate) 
{ 
var day =theDate; 
var Year = 0; 
var Month = 0; 
var Day = 0; 
var CurrentDate = ""; 
//初始化时间 
Year= day.getFullYear();//ie火狐下都可以 
Month= day.getMonth()+1; 
Day =day.getDate(); 
CurrentDate += Year + "-"; 
if (Month >= 10) 
{ 
CurrentDate += Month + "-"; 
} 
else{ 
CurrentDate += "0" + Month + "-"; 
} 
if (Day >= 10) 
{ 
CurrentDate +=Day ; 
} 
else{ 
CurrentDate += "0" +Day ; 
} 
returnCurrentDate; 
}

functiongetDateRange(_year,_week){ 
varbeginDate; 
varendDate; 
if(_year == null || _year == '' || _week == null || _week == ''){ 
return ""; 
} 
beginDate = getXDate(_year,_week,4); 
endDate = getXDate(_year,(_week - 0 + 1),5); 
return getNowFormatDate(beginDate) + " 至 "+getNowFormatDate(endDate); 
} 
 

functiongetXDate(year,weeks,weekDay){ 
//用指定的年构造一个日期对象，并将日期设置成这个年的1月1日 //因为计算机中的月份是从0开始的,所以有如下的构造方法 
var date = new Date(year,"0","1"); 
 
//取得这个日期对象 date 的长整形时间 time 
var time =date.getTime(); 
 
//将这个长整形时间加上第N周的时间偏移 //因为第一周就是当前周,所以有:weeks-1,以此类推 //7*24*3600000 是一星期的时间毫秒数,(JS中的日期精确到毫秒) 
time+=(weeks-1)*7*24*3600000; 
 
//为日期对象 date 重新设置成时间 time 
date.setTime(time); 
returngetNextDate(date,weekDay); 
} 

functiongetNextDate(nowDate,weekDay){ 
//0是星期日,1是星期一,... 
weekDay%=7; 
var day =nowDate.getDay(); 
var time =nowDate.getTime(); 
var sub = weekDay-day; 
if(sub <= 0){ 
sub += 7; 
} 
time+=sub*24*3600000; 
nowDate.setTime(time); 
returnnowDate; 
}

1 functiongetBeforeDate(n){
2     var n =n;
3     var d = newDate();
4     var year =d.getFullYear();
5     var mon=d.getMonth()+1;
6     var day=d.getDate();
7     if(day <=n){
8             if(mon>1) {
9                mon=mon-1;
10 }
11            else{
12              year = year-1;
13              mon = 12;
14 }
15 }
16           d.setDate(d.getDate()-n);
17           year =d.getFullYear();
18           mon=d.getMonth()+1;
19           day=d.getDate();
20      s = year+"-"+(mon<10?('0'+mon):mon)+"-"+(day<10?('0'+day):day);
21      returns;
22 }
23 console.log(getBeforeDate(1));//昨天的日期
24 console.log(getBeforeDate(7));//前七天的日期