[keen]

function featureRemover(s) {
    return ('' + s).replace('&feature=player_detailpage', '');
}

console.log(featureRemover('_ttp://www.youtube.com/watch?v=kBevzsFGQv8'));
// выведет: _ttp://www.youtube.com/watch?v=kBevzsFGQv8