參考如下代碼

function formatDate(date) {
   var d = new Date(date),
       month = '' + (d.getMonth() + 1),
       day = '' + d.getDate(),
       year = d.getFullYear();

   if (month.length < 2) month = '0' + month;
   if (day.length < 2) day = '0' + day;

   return [year, month, day].join('-');
}

使用方法：

console.log(formatDate('Sun May 13,2016'));

輸出：

2016-05-13

2014-05-11