Lowest number missed in an array

Given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A

by narensrinivasans

HTML

<div id="result1"></div>

JavaScript

function solution(a) {
  tempArray.sort(function(a,b){return a-b});
  tempArray = tempArray.filter(function(c){return Math.min(c)})
	return tempArray;
}

var input1 = [4,2,5,1];
document.getElementById('result1').innerHTML = solution(input1);