js 格式化时间

Date.prototype.format = function(format) {
       var date = {
              "M+": this.getMonth() + 1,
              "d+": this.getDate(),
              "h+": this.getHours(),
              "m+": this.getMinutes(),
              "s+": this.getSeconds(),
              "q+": Math.floor((this.getMonth() + 3) / 3),
              "S+": this.getMilliseconds()
       };
       if (/(y+)/i.test(format)) {
              format = format.replace(RegExp.$1, (this.getFullYear() + '').substr(4 - RegExp.$1.length));
       }
       for (var k in date) {
              if (new RegExp("(" + k + ")").test(format)) {
                     format = format.replace(RegExp.$1, RegExp.$1.length == 1
                            ? date[k] : ("00" + date[k]).substr(("" + date[k]).length));
              }
       }
       return format;
}
console.log(new Date().format('yyyy-MM-dd h:m:s'));//2018-03-28 22:03