yes but that would require server to know that which again requires some sort of ajax which cannot happen because js is disabled!

apparently I have to spell it out to the downvoter...

    <script src="/client-side.js"></script>
    <noscript><img src="/server-side.js"></noscript>

...which fulfills the requirement of "executing some JS code even if JS is disabled in browser".

yes, that seems correct, also just to make it clear, i can't even down vote yet :P so it wasn't me :)