实现下拉菜单的动画

function donghua(){
        $( '.dropdown-menu span' ).hover(//添加事件，对class dropdown-menu下的span加hover
        function(event){
            console.log(event.target.className);
            if(event.target.className == "aa"){//进行判断
                $(".dropdown").children('.aa_6').slideUp(20);//隐藏
                $(".dropdown").children('.aa_5').slideUp(20);//隐藏
                $(".dropdown").children('.aa_4').slideDown(20);//显示
            }else if(event.target.className == "cc"){
                $(".dropdown").children('.aa_6').slideUp(20);//隐藏
                $(".dropdown").children('.aa_4').slideUp(20);//隐藏
                $(".dropdown").children('.aa_5').slideDown(20);//显示
            }else if(event.target.className == "dd"){
                $(".dropdown").children('.aa_4').slideUp(20);//隐藏
                $(".dropdown").children('.aa_5').slideUp(20);//隐藏
                $(".dropdown").children('.aa_6').slideDown(20);//显示
            }else{
                $(".dropdown").children('.sub-menu').slideUp(20);//隐藏
            }                
        }
    );
}