The definition of happy number is from mathematics (see WikiPedia). Basically what is needed to know is that numbers 2-6 are unhappy, while 1 and 7 are.

```
const isHappy = n => {
let number = n;
let digit = 0;
while (number > 6) {
let sum = 0;
while(number > 0) {
digit = number % 10;
sum += Math.pow(digit, 2);
number = Math.floor(number / 10);
}
number = sum;
}
return number === 1;
}
```