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is there a way to add a class to every nth item in a menu using wp_nav_menu?

Trying to create columns but need to add a 'last' class to the 3rd item.

cheers! Dc

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Did you try this ? – mike23 Jul 13 '11 at 16:12
i need it to be automatic for the clients sake as they'll be adding new pages/post into the menu at will. So i'll always need the 3rd item to have a class 'last'. Cheers though... – daniel Crabbe Jul 13 '11 at 17:40
How are you trying to structure the Nav? – Alex Older Jul 14 '11 at 7:51
structure is <ul><li>link</li>... </ul> – daniel Crabbe Jul 14 '11 at 9:08

You can use jQuery to do that. Try this in your header :

$(document).ready(function() {
    $("#mymenu li:nth-child(3n+3)").addClass("last");

Note : for this to work you need to have enqueued jQuery.

share|improve this answer
Updated the code, it was only selecting the third element, not every third. (thx to Chris_O's answer) – mike23 Jul 14 '11 at 8:16
Cheers Mike - thought about jquery but using it wont meet our clients' requirements so it has to bee php/css. – daniel Crabbe Jul 14 '11 at 9:07

Nth is already a class, it's a pseudo class.

Why don't you just change whatever css applied to .last and apply it to #nav li:nth-child(3). If you need to target every third menu item it would be #nav li:nth-child(3n+3)


Oh yah I forgot to mention support for those pesky stone age browsers.

Luckily there are some good javascript libraries and jQuery plugins that add css3 support to IE < 9

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right but that would be a little risky as nth-child in CSS is only supported by the most recent browsers (no IE8 or FF3 for example) – mike23 Jul 14 '11 at 8:14
Yeh - really annoying all the ie browsers (<9) don't support it. IS there not a add_filter approach to this? – daniel Crabbe Jul 14 '11 at 9:07
There are plenty of javascript libraries that add css3 support for older browsers. I like selectivizr – Chris_O Jul 14 '11 at 9:37
up vote 1 down vote accepted

got this working like this in the end...

function add_nthclass($items, $args){

  $scb = get_object_vars($args);

  switch($scb['menu']) {

        case 'mainpages':
            $nth = 2;
            $items = explode('</li>',$items);
            $newitems = array();
              // loop through the menu items, and add the new link at the right position
              foreach($items as $index => $item)                  {

                if(($index+1) % $nth == 0){
                    $newitems[] =  str_replace('class="', 'class="last ', $item);
                $newitems[]= $item;                 
              // finally put all the menu items back together into a string using the ending <li> tag and return
              $newitems = implode('</li>',$newitems);

        case 'footer':
         // footer menu nth funcs...

            $newitems = $items;

    } // End switch

    return $newitems;    
add_filter('wp_nav_menu_items', 'add_nthclass', 10, 2);
share|improve this answer

If you just want to add class .last to the last menu item, this is a much shorter way to do it:

/* add .last to last menu item                            */

add_filter('wp_nav_menu', 'add_last');

function add_last($output) {
  $output = substr_replace($output, 'class="last menu-item', strripos($output, 'class="menu-item'), strlen('class="menu-item'));
  return $output;

If you also have submenus, you can use the following code (thanks to this article).

add_filter('wp_nav_menu', 'add_last');

function add_last($menuHTML) {
  $last_items_ids  = array();
  // Get all custom menus
  $menus = wp_get_nav_menus();
  // For each menu find last items
  foreach ( $menus as $menu_maybe ) {
    // Get items of specific menu
    if ( $menu_items = wp_get_nav_menu_items($menu_maybe->term_id) ) {
      $items = array();
      foreach ( $menu_items as $menu_item ) {
        $items[$menu_item->menu_item_parent][] .= $menu_item->ID;
      // Find IDs of last items
      foreach ( $items as $item ) {
        $last_items_ids[] .= end($item);
  foreach( $last_items_ids as $last_item_id ) {
    $items_add_class[] .= ' menu-item-'.$last_item_id;
    $replacement[]     .= ' menu-item-'.$last_item_id . ' last';
  $menuHTML = str_replace($items_add_class, $replacement, $menuHTML);
  return $menuHTML;
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