Arrays - Find missing numbers in a Sequence

Question

I\'m trying to find an easy way to loop (iterate) over an array to find all the missing numbers in a sequence, the array will look a bit like the one below.

var nu

Answer 1

Please check below code.....

function solution(A) {
   var max = Math.max.apply(Math, A);
   if(A.indexOf(1)<0) return 1;
   var t = (max*(max+1)/2) - A.reduce(function(a,b){return a+b});
   return t>0?t:max+1;
}