date-fns "RangeError: Invalid time value"
Your code is failing because new Date() requires a valid date time string to create a new date object. To fix this, simply formulate a current date string and attach the timestamp you require and pass it to the new Date() method. Then you can pass the date object to the format method to get the desired output.
Refer to this chart to format your dates as per your requirement.
const now = dateFns.format(new Date(), 'YYYY-MM-DD');
const custTime = '18:00:00.000';
const custDt = new Date(`${now} ${custTime}`);
console.log(dateFns.format(custDt, 'h:mm A'));<script src="https://cdnjs.cloudflare.com/ajax/libs/date-fns/2.0.0-alpha0/date_fns.min.js" integrity="sha512-0kon+2zxkK5yhflwFqaTaIhLVDKGVH0YH/jm8P8Bab/4EOgC/n7gWyy7WE4EXrfPOVDeNdaebiAng0nsfeFd9A==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>