Create Dropdown Menu

Hi,
I’m trying to create simple dropdown menu. here’s the code:
the expected:

<ul id="menu-category_menu" class="menu">
<li id="menu-item-28" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-has-children menu-item-28">
<a href="#">Produk</a>
<ul class="sub-menu" style="display:none;">
	<li id="menu-item-29" class="menu-item menu-item-type-taxonomy menu-item-object-category menu-item-29"><a href="https://gedangambon.com/category/gedang-goreng">Gedang Goreng</a></li>
</ul>
</li>
</ul>

I have menu called ‘category_menu’, if the parent menu has sub menu, I want to add tag style="display_none" inside tag ‘ul’. so I added in header.php:

wp_nav_menu(array(
'menu' => 'category_menu',
'container' => false,
'items_wrap' => '<ul id="%1$s" class="%2$s" style="display:none;">%3$s</ul>'
));

but, the result is not like what I expected:

<ul id="menu-category_menu" class="menu" style="display:none;">
<li id="menu-item-28" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-has-children menu-item-28">
<a href="#">Produk</a>
<ul class="sub-menu">
	<li id="menu-item-29" class="menu-item menu-item-type-taxonomy menu-item-object-category menu-item-29"><a href="https://gedangambon.com/category/gedang-goreng">Gedang Goreng</a></li>
</ul>
</li>
</ul>

the tag style="display:none;" appeared in parent menu.
How to insert tag style="display:none;" into submenu?
This is javascript I used to control dropdown effect:

<script>
$(document).ready(function() {
	$('#menu_container li').hover(
	    function () {
		$('ul:first', this).css('display','block');
	    },
	    function () {
		$('ul:first', this).css('display','none');
	    }
	);
});
</script>

I need help guys, thank you before.