Validate and also work with iso dates

working-with-iso-dates.js

// ==============================================
// Function validates whether passed string is valid iso format
function isIsoDate(str) {
  if (!/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}Z/.test(str)) return false;
  const d = new Date(str); 
  return d instanceof Date && !isNaN(d) && d.toISOString()===str; // valid date 
}

console.log(isIsoDate('2011-10-05T14:48:00.000Z'))

console.log(isIsoDate('2018-11-10T11:22:33+00:00'));

console.log(isIsoDate('2011-10-05T14:99:00.000Z')); // invalid time part 

// ==============================================
// Function converts iso string date to convert iso date to match local time with offset

function returnDateWithOffset(dateTime) {
// var startTimeISOString = "2013-03-10T02:00:00Z";

//   check dateTime is valid iSO date time string
//   isIsoDate()
 var newDate = new Date(dateTime);
 return  new Date(newDate.getTime() + (newDate.getTimezoneOffset() * 60000));
}