求，JS计算日期！

Question

输入参数：年份，第几周。返回参数：该周起始月日。比如：输入参数 年份2012 ，第2周。返回参数 1月8日 到 1月14日
求实现上述功能的函数。

Answer 1

第一周和最后一周怎么算？下面的代码只包括当年的日期。如果需要包括前一年/后一年的日期，稍微修改一下也不难        function getStartDateByWeek(year, week) {
            var startDate = new Date();
            startDate.setFullYear(year, 0, 1); //变态的js月份从0开始
            var dayOfWeek = startDate.getDay();
            var count = 0;
            var weekCount = 1;
            if (weekCount === week) {
                return startDate;
            }
            else {
                while (weekCount !== week) {
                    startDate.setDate(startDate.getDate() + 7);
                    weekCount++;
                }
                while (dayOfWeek > 0) {
                    startDate.setDate(startDate.getDate() - 1);
                    dayOfWeek = startDate.getDay();
                }
            }
            return startDate;
        }
得到了开始日期，结束日期只要+6就行了:        function getEndDate(startDate, year) {
            var endDate = new Date(startDate);
            if (startDate.getMonth() === 11 && startDate.getDate() > 25) {
                endDate.setFullYear(year, 11, 31);
            }
            else {
                endDate.setDate(startDate.getDate() + 6);
            }
            return endDate;
        }
如果需要包括前一年/后一年的日期，上面的代码稍微修改一下：        function getStartDateByWeek(year, week) {
            var startDate = new Date();
            startDate.setFullYear(year, 0, 1); //变态的js月份从0开始
            var dayOfWeek = startDate.getDay();
            var count = 0;
            var weekCount = 1;
            if (weekCount === week) {
                startDate.setFullYear(year - 1, 11, 31);
                dayOfWeek = startDate.getDay();
                while (dayOfWeek > 0) {
                    startDate.setDate(startDate.getDate() - 1);
                    dayOfWeek = startDate.getDay();
                }
            }
            else {
                while (weekCount !== week) {
                    startDate.setDate(startDate.getDate() + 7);
                    weekCount++;
                }
                while (dayOfWeek > 0) {
                    startDate.setDate(startDate.getDate() - 1);
                    dayOfWeek = startDate.getDay();
                }
            }
            return startDate;
        }        function getEndDate(startDate, year) {
            var endDate = new Date(startDate);
            if (startDate.getMonth() === 11 && startDate.getDate() > 25) {
                var newYear = year + 1;
                var newDate = 6 - (31 - startDate.getDate());
                endDate.setFullYear(newYear, 0, newDate);
            }
            else {
                endDate.setDate(startDate.getDate() + 6);
            }
            return endDate;
        }

Answer 2

不好意思，第2部分代码有错，重贴：        function getStartDateByWeek(year, week) {
            var startDate = new Date();
            startDate.setFullYear(year, 0, 1); //变态的js月份从0开始
            var dayOfWeek = startDate.getDay();
            var count = 0;
            var weekCount = 1;
            if (weekCount === week) {
                while (dayOfWeek > 0) {
                    startDate.setDate(startDate.getDate() - 1);
                    dayOfWeek = startDate.getDay();
                }
            }
            else {
                while (weekCount !== week) {
                    startDate.setDate(startDate.getDate() + 7);
                    weekCount++;
                }
                while (dayOfWeek > 0) {
                    startDate.setDate(startDate.getDate() - 1);
                    dayOfWeek = startDate.getDay();
                }
            }
            return startDate;
        }        function getEndDate(startDate, year) {
            var endDate = new Date(startDate);
            endDate.setDate(startDate.getDate() + 6);
            return endDate;
        }

Answer 3

function fun(year, week){
var d1, d2;
if(week == 1){
d1 = new Date(year, 0, 1);
d2 = new Date(d1);
d2.setDate(d2.getDate() + (6 - d2.getDay()));
} else {
d1 = new Date(year, 0, 1);
d1.setDate(d1.getDate() + (0 - d1.getDay()) + (7 * (week - 1)));
d2 = new Date(d1);
d2.setDate(d2.getDate() + 6);
} var ret = 
{
StartDate: d1,
EndDate: d2
};
return ret;
}var ret = fun(2012, 2);
var d1M = ret.StartDate.getMonth() + 1;
var d1D = ret.StartDate.getDate();
alert("起始日期是：" + d1M + "月" + d1D + "日");
var d2M = ret.EndDate.getMonth() + 1;
var d2D = ret.EndDate.getDate();
alert("结束日期是：" + d2M + "月" + d2D + "日");

Answer 4

漏了一点function fun(year, week){
var d1, d2;
if(week == 1){
d1 = new Date(year, 0, 1);
d2 = new Date(d1);
d2.setDate(d2.getDate() + (6 - d2.getDay()));
} else {
d1 = new Date(year, 0, 1);
d1.setDate(d1.getDate() + (0 - d1.getDay()) + (7 * (week - 1)));
d2 = new Date(d1);
d2.setDate(d2.getDate() + 6);
while(d2.getFullYear() != d1.getFullYear()) {
d2.setDate(d2.getDate() - 1);
}
} var ret = 
{
StartDate: d1,
EndDate: d2
};
return ret;
}