日期格式化和获取本周、本季度、本月、上月的开端日期、停止日期

/**
 * 获取本周、本季度、本月、上月的开端日期、停止日期
 */
var now = new Date(); // 当前日期
var nowDayOfWeek = now.getDay(); // 今天本周的第几天
var nowDay = now.getDate(); // 当前日
var nowMonth = now.getMonth(); // 当前月
var nowYear = now.getYear(); // 当前年
nowYear += (nowYear < 2000) ? 1900 : 0; // 

var lastMonthDate = new Date(); // 上月日期
lastMonthDate.setDate(1);
lastMonthDate.setMonth(lastMonthDate.getMonth() - 1);
var lastYear = lastMonthDate.getYear();
var lastMonth = lastMonthDate.getMonth();

// 格局化日期：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);
}

// 获得某月的天数
function getMonthDays(myMonth) {
    var monthStartDate = new Date(nowYear, myMonth, 1);
    var monthEndDate = new Date(nowYear, myMonth + 1, 1);
    var days = (monthEndDate - monthStartDate) / (1000 * 60 * 60 * 24);
    return days;
}

// 获得本季度的开端月份
function getQuarterStartMonth() {
    var quarterStartMonth = 0;
    if (nowMonth < 3) {
        quarterStartMonth = 0;
    }
    if (2 < nowMonth && nowMonth < 6) {
        quarterStartMonth = 3;
    }
    if (5 < nowMonth && nowMonth < 9) {
        quarterStartMonth = 6;
    }
    if (nowMonth > 8) {
        quarterStartMonth = 9;
    }
    return quarterStartMonth;
}

// 获得本周的开端日期
function getWeekStartDate() {
    var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek);
    return formatDate(weekStartDate);
}

// 获得本周的停止日期
function getWeekEndDate() {
    var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek));
    return formatDate(weekEndDate);
}

// 获得本月的开端日期
function getMonthStartDate() {
    var monthStartDate = new Date(nowYear, nowMonth, 1);
    return formatDate(monthStartDate);
}

// 获得本月的停止日期
function getMonthEndDate() {
    var monthEndDate = new Date(nowYear, nowMonth, getMonthDays(nowMonth));
    return formatDate(monthEndDate);
}

// 获得上月开端时候
function getLastMonthStartDate() {
    var lastMonthStartDate = new Date(nowYear, lastMonth, 1);
    return formatDate(lastMonthStartDate);
}

// 获得上月停止时候
function getLastMonthEndDate() {
    var lastMonthEndDate = new Date(nowYear, lastMonth, getMonthDays(lastMonth));
    return formatDate(lastMonthEndDate);
}

// 获得本季度的开端日期
function getQuarterStartDate() {

    var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);
    return formatDate(quarterStartDate);
}

// 或的本季度的停止日期
function getQuarterEndDate() {
    var quarterEndMonth = getQuarterStartMonth() + 2;
    var quarterStartDate = new Date(nowYear, quarterEndMonth,
            getMonthDays(quarterEndMonth));
    return formatDate(quarterStartDate);
}
//日期格式化
Date.prototype.pattern = function(fmt) {
    var o = {
        "M+" : this.getMonth() + 1, // 月份
        "d+" : this.getDate(), // 日
        "h+" : this.getHours() % 12 == 0 ? 12 : this.getHours() % 12, // 小时
        "H+" : this.getHours(), // 小时
        "m+" : this.getMinutes(), // 分
        "s+" : this.getSeconds(), // 秒
        "q+" : Math.floor((this.getMonth() + 3) / 3), // 季度
        "S" : this.getMilliseconds()
    // 毫秒
    };
    var week = {
        "0" : "/u65e5",
        "1" : "/u4e00",
        "2" : "/u4e8c",
        "3" : "/u4e09",
        "4" : "/u56db",
        "5" : "/u4e94",
        "6" : "/u516d"
    };
    if (/(y+)/.test(fmt)) {
        fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "")
                .substr(4 - RegExp.$1.length));
    }
    if (/(E+)/.test(fmt)) {
        fmt = fmt
                .replace(
                        RegExp.$1,
                        ((RegExp.$1.length > 1) ? (RegExp.$1.length > 2 ? "/u661f/u671f"
                                : "/u5468")
                                : "")
                                + week[this.getDay() + ""]);
    }
    for ( var k in o) {
        if (new RegExp("(" + k + ")").test(fmt)) {
            fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k])
                    : (("00" + o[k]).substr(("" + o[k]).length)));
        }
    }
    return fmt;
}