convert mm/dd/yy into date format 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: javascript date parse yyyy-mm-dd

var dateString = "10/23/2015"; // Oct 23

var dateObject = new Date(dateString);

document.body.innerHTML = dateObject.toString();