add_action( 'wp', 'homepage_mobile_redirect' );
function homepage_mobile_redirect() {
    if ( wp_is_mobile() AND is_front_page() ) {
        wp_redirect( '/mobileshop/', 301 );
        exit;
    }
}


-or-
  
  
  if (document.documentElement.clientWidth <760) {
 window.location = "/webshop";
}