The date and time of return method

. 1  / * *
 2  　　FMT is returned to the pre-format time. For example: "yyyy-MM-dd HH: mm: SS q" ==> 2019-12-17 14:15:16 4
 3  　　　　　　　　　　　　　　　　　　　　"YY MM month in the first quarter q dd Day" ==> January 1, 2018 Q1 
 . 4  　　DATE a Date type
 . 5  * / 
. 6 const = dateTime (FMT, DATE) => { 
 . 7      the let O = {
 . 8        "M +": date.getMonth () + 1 ,    
 . 9        "D +" : date.getDate () ,   
 10        "H +" : date.getHours (),   
 . 11        "m +" : date.getMinutes (),   
 12 is        "+ S" : date.getSeconds (),  
       "q+": Math.floor((date.getMonth() + 3) / 3),  
14       "S": date.getMilliseconds()  
15     };
16     if (/(y+)/.test(fmt))
17       fmt = fmt.replace(RegExp.$1, (date.getFullYear() + "").substr(4 - RegExp.$1.length));
18     for (let k in o)
19       if (new RegExp("(" + k + ")").test(fmt))
20         fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
21     return fmt;
22   }