Question

E.g. dropdown menu if yo render it and quickly mouse over the “about us” button and out like 5 times and stop menu going to open several times and then stop. I need it to just do the last one animation.

<script type="text/javascript">
    $(document).ready(function(){
        $("ul.topnav li a").mouseenter(function() {
            $(this).parent().find("ul.subnav").slideDown('fast').show();
        });  


        $(".dropdown").mouseleave(function(){ 
            $(this).stop(true, false);
            $(this).parent().find("ul.subnav").slideUp('fast');
        });
    });

HTML:

<ul class="topnav">  
    <li><a href="#">Home</a></li>  
    <li class="dropdown">  
        <a href="#">About Us</a>  
        <ul class="subnav dropdown">  
            <li><a href="#">Sub Nav Link 1</a></li>  
            <li><a href="#">Sub Nav Link 2</a></li>  
        </ul>
    </li>  
</ul>
</script>

Answer 1

Prefix your transition with .stop(true, true), e.g.:

$(this).parent().find("ul.subnav").stop(true, true).slideDown('fast').show();