A jQuery drop-down menu with simple code

I recently discovered a simple jQuery drop-down menu with very little code, which is very suitable for beginners with basic knowledge to learn and improve.
This is the jQuery code:

<script type="text/javascript"> 
$(document).ready(function(){ 
    $("ul.subnav").parent().append("<span></span>"); 
    
    $("ul.topnav li span").click(function() { 
        $(this).parent().find("ul.subnav").slideDown(&#39;fast&#39;); 
        $(this).parent().hover(function() { 
        }, function(){    
            $(this).parent().find("ul.subnav").slideUp(&#39;slow&#39;); 
        }); 
    
        }).hover(function() { 
            $(this).addClass("subhover"); 
        }, function(){    //On Hover Out 
            $(this).removeClass("subhover"); 
    }); 
}); 
</script>

The following is the html code:

<div id="header"> 
        
        <ul class="topnav"> 
            <li><a href="#">首页</a></li> 
            <li> 
                <a href="#">原创作品</a> 
                <ul class="subnav"> 
                    <li><a href="#">绘画艺术</a></li> 
                    <li><a href="#">平面设计</a></li> 
                    <li><a href="#">交互设计</a></li> 
                    <li><a href="#">3D艺术</a></li> 
                    <li><a href="#">摄影艺术</a></li> 
                    <li><a href="#">其他艺术</a></li> 
                </ul> 
            </li> 
            <li> 
                <a href="#">设计素材</a> 
                <ul class="subnav"> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                </ul> 
            </li> 
            <li> 
                <a href="#">佳作欣赏</a> 
                <ul class="subnav"> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                    <li><a href="#">Sub Nav Link</a></li> 
                </ul> 
            </li> 
            <li><a href="#">论坛</a></li> 
            <li><a href="#">网址导航</a></li> 
        </ul> 
    </div>

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