ArraySearch - JavascriptModule0

// Array Search
// Given an array of integers, some elements appear twice and others appear once. Each integer is in the range of 1, N,
// where N is the number of elements in the array.
// Find all the integers of 1, N inclusive that do NOT appear in this array.
// Input
// Read from the standard input:
// There is one line of input, containing N amount of integers, seperated by a comma (",")
// Output
// Print to the standard output:
// There is one line of output, containing the sorted integers, seperated by a comma (",")
// Constraints
// N will always be in the range of 5, 1000
// Sample Tests
// Input
// 1,2,3,3,5
// Output
// 4
// Input
// 4,3,2,7,8,2,3,1
// Output
// 5,6
// Input
// 1,1,1,1,1,1,1,1
// Output
// 2,3,4,5,6,7,8
// CREDIT TO: https://codereview.stackexchange.com/questions/220516/find-all-numbers-disappeared-in-an-array
const input = ['3,1,1,5,1,1,1,5,1'];
const print = this.print || console.log;
const gets = this.gets || ((arr, index) => () => arr[index++])(input, 0);
const arrOfItems = gets().split(',').map(Number);
function findMissing (arr) {
  const set = new Set(arr);
  const result = [];
  let i = arr.length;
  while (i) {
    set.has(i--) || result.push(i + 1);
  }
  return result.sort((a, b) => a - b);
}
print(findMissing(arrOfItems).join(','));