jQuery(document).ready(function($) {

    var AjaxRunning = 0;

    $('form').submit(function(event){

        event.preventDefault();

        if( !AjaxRunning ){

            $.ajax({
                type: 'POST',
                url: AJAX.url,
                data: {
                    action: 'my_ajax_function',
                    nonce: AJAX.nonce,
                },
                dataType: 'json',
                beforeSend: function(){
                    AjaxRunning++;
                },
                success: function( result ) {
                    if (result.success) {
                        console.log( 'success' + AjaxRunning );
                    }
                },
                complete: function(){
                    AjaxRunning--;
                }
            });

        }

    });

});