tryCatch.js

function weekDay(dayNum) {
  if (dayNum < 1 || dayNum > 7) {
    throw 'InvalidDayNumber'
  } else {
    return ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'][dayNum - 1];
  }
}

try { // Try to run the following
  let day = weekDay(8);
  console.log(day);
}
catch (e) { // catch an error if the above try failed
  let day = 'unknown';
  console.log(e);
}