javascript求上一周和下一周

function getLastWeek_Clicked(){
    var now = new Date();
    var n = now.getDay();
    var start = new Date();
    var end = new Date();
    start.setDate(now.getDate() - n - 6);//取得上周内的第一天
    end.setDate(now.getDate() - n + 0);//取得上周内的第七天
    $("#startDateTime").val(start.format("yyyy-MM-dd"));
    $("#endDateTime").val(end.format("yyyy-MM-dd"));
}
function getNextWeek_Clicked(){
    var now = new Date();
    var n = now.getDay();
    var start = new Date();
    var end = new Date();
    start.setDate(now.getDate() - n +8 );//取得下周内的第一天
    end.setDate(now.getDate() - n + 14);//取得下周内的第七天
    $("#startDateTime").val(start.format("yyyy-MM-dd"));
    $("#endDateTime").val(end.format("yyyy-MM-dd"));
}
function getThisWeek_Clicked(){    
        var now = new Date();
        var n = now.getDay();
        var start = new Date();
        var end = new Date();
        start.setDate(now.getDate() - n + 1);//取得本周内的第一天
        end.setDate(now.getDate() - n + 7);//取得本周内的第七天
        $("#startDateTime").val(start.format("yyyy-MM-dd"));
        $("#endDateTime").val(end.format("yyyy-MM-dd"));
}
function openMeeting(meetingId, meetingName){
    var strUrl = contextPath + "/meetingAction.do?action=open&id=" + meetingId;
    OZ.openWindow({
        id: "meeting_" + new Date().getTime(),
        title: meetingName,
        url: strUrl, 
        refresh: true,
        beforeCloseFnName: "oz_Win_BeforeClose"
    });
}
Date.prototype.format = function(format){ 
    var o = { 
    "M+" : this.getMonth()+1, //month 
    "d+" : this.getDate(), //day 
    "h+" : this.getHours(), //hour 
    "m+" : this.getMinutes(), //minute 
    "s+" : this.getSeconds(), //second 
    "q+" : Math.floor((this.getMonth()+3)/3), //quarter 
    "S" : this.getMilliseconds() //millisecond 
    }
    if(/(y+)/.test(format)) { 
        format = format.replace(RegExp.$1, (this.getFullYear()+"").substr(4 - RegExp.$1.length)); 
        } 
        for(var k in o) { 
        if(new RegExp("("+ k +")").test(format)) { 
        format = format.replace(RegExp.$1, RegExp.$1.length==1 ? o[k] : ("00"+ o[k]).substr((""+ o[k]).length)); 
        } 
        } 
        return format; 
}