JSFiddle - React, Tailwind, and code Playground

by dshilkret

JavaScript

var arr = [1, 3, 6, 4, 1, 2];
function getNum(n) {
  const set = new Set(n);
  let i = 1;

  while (set.has(i)) {
    i++;
  }
  alert(i);
  return i;
}

getNum(arr);