Fastest way - infinite loop
```javascript []
/**
 * @param {string} s
 * @return {boolean}
 */
var hasSameDigits = function(s) {
    arr = [...s]

    while (arr.length > 2) {
        arr = newDigit(arr)
    }

    return arr[0] == arr[1]
};

function newDigit(ar) {
    temp = []

    for (let i = 0; i < ar.length - 1; i++) {
        temp.push((~~ar[i] + ~~ar[i+1])  % 10)
    }

    return temp
}
```
['JavaScript']