wordpress add admin menu item post ajax request on button press

wp-admin-menu-ajax-request

//add a menu page with a button to do stuff
add_action('admin_menu', 'my_menu_pages');
function my_menu_pages(){
    add_menu_page('Actualizar Liga Magus', 'Actualizar Liga', 'manage_options', 'my-menu', 'my_menu_output','',0 );
}
function my_menu_output(){
	$html = '<a href="#ajaxthing" class="myajax">Teste</a>';
	echo $html;
}
add_action('admin_head', 'my_action_javascript');
function my_action_javascript() {
?>
<script type="text/javascript" >
	jQuery(document).ready(function($) {
			let value = 1234;
			$('.myajax').click(function(){
					var data = {
							action: 'my_function_name',
							whatever: value
					};
					// since 2.8 ajaxurl is always defined in the admin header and points to admin-ajax.php
					$.post(ajaxurl, data, function(response) {
							value = value + response;
							alert('Got this from the server: ' + response);
					});
			});
	});
</script>
<?php
}
add_action('wp_ajax_my_function_name', 'my_exec_me');
function my_exec_me() {
     //global $wpdb; // this is how you get access to the database
     $whatever = $_POST['whatever'];
     $whatever += 10;
    echo $whatever;
     exit(); // this is required to return a proper result & exit is faster than die();
}