CODE EXAMPLE FOR JAVASCRIPT

Codewars 1n- Cycle

function cycle(n) {
    if (n % 2 == 0 || n % 5 == 0) return -1;
    let i = 0, val = 1;
    while (++i) {
        val = val * 10 % n;
        if (val == 1) return i;
    }
}