Overriding pseudo styles in jQuery

How can I overwrite the CSS below with jQuery?

(The animations开发者_如何学Go aren't being run and it's just an instantaneous switch.)

menu span ul {display: none;}
menu span:hover ul {display: block;}

$('#menu span').mouseenter(function(){
    $('#menu span ul').slideDown('fast');
}).mouseleave(function(){
    $('#menu span ul').slideUp('fast');
});

One trick for graceful degredation is to not have to override the styles, like this:

<noscript>
  <style type="text/css">#menu span:hover ul {display: block;}</style>
</noscript>

Of have a linked stylesheet the same way with all of these for-non-JS-user styles.

Or, do it via a class you apply to #menu that you can remove so the rules no longer match, like this:

#menu span ul {display: none;}
#menu.noJS span:hover ul {display: block;}

And in your script just remove that class:

$("#menu").removeClass("noJS");

As a side note, you can slim down your code using .hover() and .slideToggle() like this:

$('#menu span').hover(function(){
  $(this).find('ul').slideToggle('fast');
});

You're not seeing the animation because your css is overriding it.

Remove

menu span:hover ul {display: block;}

I wouldn't bother trying to override the css to accommodate browsers that don't have js enabled. The number is so small that it isn't worth consideration.