100% solution for Missing Integer Task on Codility

MissingInteger.js

function solution(A) {
  var max = 0;
  var array = [];
  
  for (var i = 0; i < A.length; i++) {
    if (A[i] > 0) {
      if (A[i] > max) {
        max = A[i];
      }
      array[A[i]] = 0;
    }
  }
  
  if (max < 1) {
    return 1;
  }
  
  for (var j = 1; j < max; j++) {
    if (typeof array[j] === "undefined") {
      return j;
    }
  }
  
  return max + 1;
}

`
function solution(A) {
const set = new Set(A);
let missing = 1;

while(true) {
    if (set.has(missing)) {
        missing++;
    } else {
        break;
    }
}

return missing;

}
`

@ZeroGDrive spot on 💯