one-page-wordpress-script.js

(function( $ ) {
    const marginTop = 170; // puedes cambiar el margen
    const currentClasses = 'current-menu-item current_page_item';

    if ( ! window.location.hash ){
        $('li').removeClass(currentClasses);
        $('li:first-child').addClass(currentClasses);
    }

    $('li a[href*="#"]').click(function(event) {
        const link = this;
        let target = $(link.hash);

        event.preventDefault();
        target = target.length ? target : $('[name=' + this.hash.slice(1) + ']');

        $('html, body').animate({
            scrollTop: target.offset().top - marginTop
            }, 1000, function() {
                $('li').removeClass(currentClasses);
                $(link).parent().addClass(currentClasses);
            });
    });

})( jQuery );