javascript 时间戳转日期格式

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;
    }

    var testDate = new Date( 1320336000000 );//这里必须是整数，毫秒

    var testStr = testDate.format("yyyy年MM月dd日hh小时mm分ss秒");
    var testStr2 = testDate.format("yyyyMMdd hh:mm:ss");
    alert(testStr + "   " + testStr2);