Ajax

https://api.jquery.com/jQuery.ajax/

/*enqueue localize*/
wp_enqueue_script('script-js', get_template_directory_uri() . '/js/script.js', array('jquery'), '1.0.0', false);
    //ajax
    wp_localize_script( 'script-js', 'frontend_ajax_object',
        array( 
            'home' => get_option('home'),
        )
    );

/*script pkb*/
var $obj_id = $('.single-salon-collection .num').attr('id');
$.ajax({
url: frontend_ajax_object.home + '/salon-collection/',
context: document.body
}).done(function(data) {
var $number = $(data).find('#' + $obj_id).find('.order').html();
$('.single-salon-collection .num').html($number);
});