CODE EXAMPLE FOR JAVASCRIPT

missing num

const findMissing = num => {
  const max = Math.max(...num); // Will find highest number
  const min = Math.min(...num); // Will find lowest number
  const missing = []

  for(let i=min; i<= max; i++) {
    if(!num.includes(i)) { // Checking whether i(current value) present in num(argument)
      missing.push(i); // Adding numbers which are not in num(argument) array
    }
  }
  return missing;
}

findMissing([1,15]);