isDevisible

isDevisible.js

isDevisible = (s, t) => {
    let l = 0;
    let r = 0;
    let repStart = 0;
    
    while(l < s.length) {
        if (s[l] === t[r]) {
            l++;
            r++;
        } else if (t[r] === undefined) {
            repStart = r;
            r = 0;
        } else {
            return -1;
        }
    }

    if (repStart === 0) {
        return l % r === 0 ? r : -1;
    } else if (l % repStart === 0) {
        return repStart;
    }

    return -1
}