input user string as date in js code example

Example 1: javascript convert date to yyyy-mm-dd

// `date` is a `Date` object
const formatYmd = date => date.toISOString().slice(0, 10);

// Example
formatYmd(new Date());      // 2020-05-06

Example 2: jquery format date

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('-');
 }
 alert(formatDate('05/08/2015'));