100% solution for Permutation Missing Element on Codility

PermMissingElem.js

function solution(A) {
  if (A.length == 0) return 1;
  var min = 100000;
  var max = 0;
  var B = [];

  for (var i = 0; i < A.length; i++) {
    B[A[i]] = 0;
    if (A[i] > max) max = A[i];
    if (A[i] < min) min = A[i];
  }

  if (min != 1) return 1;
  if (max == A.length) return max + 1;

  for (; min <= max; min++) {
    if (typeof B[min] === "undefined") return min;
  }
}