Question

WordPress outputs my child menus inside this ul tag…

<ul class="sub-menu">

how can I wrap a simple div around it?

Preferably a way to do it through functions.php, but jquery can work too.

Answer 1

While it would be EASY to use something like jQuery to wrap your child menus, it is NOT good practice to use jQuery for this purpose. Place this in functions.php:

class Child_Wrap extends Walker_Nav_Menu
{
    function start_lvl(&$output, $depth = 0, $args = array())
    {
        $indent = str_repeat("\t", $depth);
        $output .= "\n$indent<div class=\"custom-sub\"><ul class=\"sub-menu\">\n";
    }
    function end_lvl(&$output, $depth = 0, $args = array())
    {
        $indent = str_repeat("\t", $depth);
        $output .= "$indent</ul></div>\n";
    }
}

I’m assuming that your menu is being generated in your header, so go to header.php (or whatever file is utilizing the wp_nav_menu function) and look for anything that starts with “wp_nav_menu”.

Since I don’t have any code to see, I can only guess the arguments that it’s using (if any). If it looks EXACTLY like “wp_nav_menu()” with nothing in between the parenthesis, then change it to the following:

wp_nav_menu(array('walker' => new Child_Wrap()))

Otherwise, please edit your question with the code that your menu is using so I can help you further.