WordPress: add HTML to a specific nav menu - php

Question

add_filter('wp_nav_menu_items', 'add_custom', 10, 2);
function add_custom($items, $args) {
if ($args->theme_location == 'primary') {
$items .= '<li class="custom"></li>';
}
return $items;
}
which produces:
<ul id="menu-top">
<li></li>
<li></li>
<li></li>
<li class="custom"></li> /* added custom HTML */
<ul>
but what if my WP menu doesn't have a "theme_location"? Can I target my menu by id/class instead of "theme_location", or how else can I add HTML to one specific menu?

Answer 1

Can you use jQuery?
jQuery(document).ready(function($) {
$('#menu-top').append('<li class="custom"></li>');
});
Or PHP + CSS - with this solution, you add it to every menu and hide it if need be via CSS.
add_filter('wp_nav_menu_items', 'add_custom', 10, 2);
function add_custom($items, $args) {
$items .= '';
return $items;
}
li.custom { display:none; } // hide originally
ul#menu-top li.custom { display:inline; } // or whatever styles

Answer 2

When there is no theme_location, then I guess, it falls back to wp_page_menu. So, in theory, you could filter into wp_page_menu and modify the output.
<?php
//Use this filter to modify the complete output
//You can get an argument to optionally check for the right menu
add_filter( 'wp_page_menu', 'my_page_menu', 10, 2 );
/**
* Modify page menu
* #param string $menu HTML output of the menu
* #param array $args Associative array of wp_page_menu arguments
* #see http://codex.wordpress.org/Function_Reference/wp_page_menu
* #return string menu HTML
*/
function my_page_menu( $menu, $args ) {
//see the arguments
//Do something with $menu
return $menu;
}
//Use this filter to alter the menu argument altogether
//It is fired before creating any menu html
add_filter( 'wp_page_menu_args', 'my_page_menu_pre_arg', 10, 1 );
/**
* Modify page menu arguments
* #param array $args Associative array of wp_page_menu arguments
* #see http://codex.wordpress.org/Function_Reference/wp_page_menu
* #return array modified arguments
*/
function my_page_menu_pre_arg( $args ) {
//Do something with $args
return $args;
}
Hope it helps.