js怎么格式化日期

Date.prototype.format = function(fmt) {

     var o = {

        "M+" : this.getMonth()+1,                 //月份

        "d+" : this.getDate(),                    //日

        "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

    };

    if(/(y+)/.test(fmt)) {

            fmt=fmt.replace(RegExp.$1, (this.getFullYear()+"").substr(4 - RegExp.$1.length));

    }

     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;

}

var time1 = new Date().format("yyyy-MM-dd hh:mm:ss");

console.log(time1);

var time2 = new Date().format("yyyy-MM-dd");

console.log(time2);

var oldTime = (new Date("2012/12/25 20:11:11")).getTime();

var curTime = new Date(oldTime).format("yyyy-MM-dd");

console.log(curTime);