javascript - How to convert js timestamp to time format

<code>//设定时间格式化函数
    Date.prototype.format = function (format) {
        var args = {
            "M+": this.getMonth() + 1,
            "d+": this.getDate(),
            "h+": this.getHours(),
            "m+": this.getMinutes(),
            "s+": this.getSeconds(),
        };
        if (/(y+)/.test(format))
            format = format.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
        for (var i in args) {
            var n = args[i];
            if (new RegExp("(" + i + ")").test(format))
                format = format.replace(RegExp.$1, RegExp.$1.length == 1 ? n : ("00" + n).substr(("" + n).length));
        }
        return format;
    };</code>