Converting milliseconds to minutes and seconds with Javascript

function millisToMinutesAndSeconds(millis) {
  var minutes = Math.floor(millis / 60000);
  var seconds = ((millis % 60000) / 1000).toFixed(0);
  return minutes + ":" + (seconds < 10 ? '0' : '') + seconds;
}

millisToMinutesAndSeconds(298999); // "4:59"
millisToMinutesAndSeconds(60999);  // "1:01"

As User HelpingHand pointed in the comments the return statement should be:

return (
  seconds == 60 ?
  (minutes+1) + ":00" :
  minutes + ":" + (seconds < 10 ? "0" : "") + seconds
);