since.2006  

直接上代码，其实就是围绕毫秒数做一些运算。

演示见：这里。

function WeekDate() {

    /**
     * 基准时间，所有计算以此为基础
     */
    var _calcDate = new Date();

    /**
     * 一天的豪秒数
     */
    var _day = 1000 * 60 * 60 * 24;

    this.getThisWeekDate = getThisWeekDate;
    this.getPrevWeekDate = getPrevWeekDate;
    this.getNextWeekDate = getNextWeekDate;
    this.wrapDate = wrapDate;

    this.getDayMillisecond = getDayMillisecond;

    /**
     * 取上周开始至上周结束日期
     *
     * @return Array [0]上周第一天 [1]上周最后一天
     */
    function getPrevWeekDate() {
        // 取上周结束日期
        var lastDay = new Date(_calcDate - (_calcDate.getDay()) * _day);
        // 取上周开始日期
        var firstDay = new Date((lastDay * 1) - 6 * _day);
        // 更新基准时间
        _calcDate = firstDay;

        return [wrapDate(firstDay), wrapDate(lastDay)];
    }

    /**
     * 取下周开始至下周结束日期
     *
     * @return Array [0]上周第一天 [1]上周最后一天
     */
    function getNextWeekDate() {
        // 取下周开始日期
        var firstDay = new Date((_calcDate * 1) + (6 - _calcDate.getDay() + 2) * _day);
        // 取下周结束日期
        var lastDay = new Date((firstDay * 1) + 6 * _day);
        // 更新基准时间        
        _calcDate = firstDay;

        return [wrapDate(firstDay), wrapDate(lastDay)];
    }

    /**
     * 取本周开始至本周结束日期
     *
     * @return Array [0]本周第一天 [1]本周最后一天
     */
    function getThisWeekDate() {
        _calcDate = new Date();
        // 第一天日期
        var firstDay = new Date(_calcDate - (_calcDate.getDay() - 1) * _day);
        // 最后一天日期
        var lastDay = new Date((firstDay * 1) + 6 * _day);

        return [wrapDate(firstDay), wrapDate(lastDay)];
    }

    function wrapDate($date) {
        var m = $date.getMonth() + 1;
        m = m < 10 ? "0" + m : m;

        var d = $date.getDate();
        d = d < 10 ? "0" + d : d;

        return $date.getFullYear() + "-" + m + "-" + d;            
    }

    function getDayMillisecond() {
        return _day;
    }
}

//var weekDate = new WeekDate();
//alert(weekDate.getNextWeekDate());
//alert(weekDate.getNextWeekDate());
//alert(weekDate.getThisWeekDate());
//alert(weekDate.getPrevWeekDate());
//alert(weekDate.getPrevWeekDate());