JavaScriptでタイムスタンプ関数をフォーマットする方法（コード付き）

 formatDate(v) {
          if (/^(-)?\d{1,10}$/.test(v))
           {
             v = v * 1000;
           } 
           else if (/^(-)?\d{1,13}$/.test(v))
            {
              v = v * 1;
            }               
            var dateObj = new Date(v);               
            var month = dateObj.getMonth() + 1;               
             var day =  dateObj.getDate();               
            var hours = dateObj.getHours();               
            var minutes = dateObj.getMinutes();               
            var seconds = dateObj.getSeconds();               
            if(month<10){
                   month = "0" + month;
               }               
            if(day<10){
                   day = "0" + day;
               }               
             if(hours<10){
                   hours = "0" + hours;
               }               
             if(minutes<10){
                   minutes = "0" + minutes;
               }               
             if(seconds<10){
                   seconds = "0" + seconds;
               }               
             var UnixTimeToDate = dateObj.getFullYear() + &#39;-&#39; + month + &#39;-&#39; +day + &#39; &#39; + hours + &#39;:&#39; + minutes + &#39;:&#39; + seconds;               
             return UnixTimeToDate;
            }