1071-greatest-common-divisor-of-strings.ts

function gcdOfStrings(str1: string, str2: string): string {
    let [len1, len2] = [str1.length, str2.length];

    function isDivisor(l: number): boolean {
        if (len1 % l || len2 % l) {
            return false;
        }

        let [f1, f2] = [Math.floor(len1 / l), Math.floor(len2 / l)];

        return (
            str1.slice(0, l).repeat(f1) == str1 &&
            str1.slice(0, l).repeat(f2) == str2
        );
    }

    for (let l = Math.min(len1, len2); l > 0; l--) {
        if (isDivisor(l)) {
            return str1.slice(0, l);
        }
    }

    return '';
}