添加背景透明度过度

Obj.hover(function(){
        
        $(this).css({"background":"rgba(0,0,0,.2)"});
        
    },function(){
        $(this).css({"background":"rgba(0,0,0,0)"});
 
    })

object{
    transition:all .5s;
                            
    background-color: rgba(#000,0);
}