需注意Date()中的月是从0开始的

  • 根据年月取周数和周一到周五的日期
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    	/**
         * 根据年月取周数和周一到周五的日期
         * @param year
         * @param month
         */
        function getInfo(year, month) {
            var result=[];
            var d = new Date();
            // what day is first day
            d.setFullYear(year, month-1, 1);
            var w1 = d.getDay();
            if (w1 == 0) w1 = 7;
            // total day of month
            d.setFullYear(year, month, 0);
            var dd = d.getDate();
            // first Monday
            var d1,week_count;
            if (w1 != 1) d1 = 7 - w1 + 2;
            else d1 = 1;
            week_count = Math.ceil((dd-d1+1)/7);//周数
            result[0]=week_count;
    //        document.write(year + "年" + month + "月有" + week_count +"周");
            for (var i = 0; i < week_count; i++) {
                var monday = d1+i*7;
                var sunday = monday + 6;
                var from = year+"/"+month+"/"+monday;
                var to;
                if (sunday <= dd) {
                    to = year+"/"+month+"/"+sunday;
                } else {
                    d.setFullYear(year, month-1, sunday);
                    to = d.getFullYear()+"/"+(d.getMonth()+1)+"/"+d.getDate();
                }
                document.write("第"+(i+1)+"周 从" + from + " 到 " + to + "");
            }
            return result;
        }
  • 根据年月日判断是一年中的第几周
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    /**
     * 判断年份是否为润年
     *
     * @param {Number} year
     */
    function isLeapYear(year) {
        return (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0);
    }
    /**
     * 获取某一年份的某一月份的天数
     *
     * @param {Number} year
     * @param {Number} month
     */
    function getMonthDays(year, month) {
        return [31, null, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month] || (isLeapYear(year) ? 29 : 28);
    }
    /**
     * 获取某年的某天是第几周
     * @param {Number} y
     * @param {Number} m
     * @param {Number} d
     * @returns {Number}
     */
    function getWeekNumber(y, m, d) {
        var now = new Date(y, m - 1, d),
            year = now.getFullYear(),
            month = now.getMonth(),
            days = now.getDate();
        //那一天是那一年中的第多少天
        for (var i = 0; i < month; i++) {
            days += getMonthDays(year, i);
        }

        //那一年第一天是星期几
        var yearFirstDay = new Date(year, 0, 1).getDay() || 7;

        var week = null;
        if (yearFirstDay == 1) {
            week = Math.ceil(days / yearFirstDay);
        } else {
            days -= (7 - yearFirstDay + 1);
            week = Math.ceil(days / 7) + 1;
        }

        return week;
    }