Question from the General knowledge for developers test

What is the fastest language for encoding and decoding Base 64 ?

    //...
    var s_encoded = 0;
    const start = new Date();
    for (var i = 0; i < TRIES; i++) {
        s_encoded += b.toString('base64').length;
    }
    const t_encoded = ((new Date()) - start) / 1000;
    //...