Happy Number

Problem

Given a number num, determine if it is a happy number.

A 'happy' number is defined as follows: Start 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.

Examples

isHappyNumber(7) 
// returns true
// 7^2 -> 49
// 4^2 + 9^2 -> 97
// 9^2 + 7^2 -> 130
// 1^2 + 3^2 + 0^2 -> 10
// 1^2 + 0^2 = 1.

isHappyNumber(11) 
// returns false
// Squaring and summing the digits of 11 does not lead to 1