how to convert yyyy mm dd to javascript 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: javascript format date yyyy-mm-dd hh:mm:ss to dd-mm-yyyy hh:mm am/pm

dateString = '2020-04-03 20:30:55';

function formatDate(dateString)
    {
        var allDate = dateString.split(' ');
        var thisDate = allDate[0].split('-');
        var thisTime = allDate[1].split(':');
        var newDate = [thisDate[2],thisDate[1],thisDate[0] ].join("-");

        var suffix = thisTime[0] >= 12 ? "PM":"AM";
        var hour = thisTime[0] > 12 ? thisTime[0] - 12 : thisTime[0];
        var hour =hour < 10 ? "0" + hour : hour;
        var min = thisTime[1] ;
        var sec = thisTime[2] ;
        var newTime = hour + ':' + min + suffix;

        return newDate + ' ' + newTime;
    }