leetcode 202 - happy number

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 

Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function(n) {
    if(n < 1){return false;}
    var sum = 0, s = String(n), result = [];
    while(true){
        sum = 0;
        for(let num of s){
            num = parseInt(num);
            sum += num*num;
        }
        if(sum == 1){return true;}
        if(result.indexOf(sum) != -1){return false;}

        result.push(sum);
        s = String(sum);
    }
};