Question

This is hiding everything and not excluding the selected index.

this.showGroup = function(groupIndex) {

    var $groups = $("#products > li.group");    

    // Hide all groups apart from selected index
    $groups.not(groupIndex).find(".scroller").hide();

    // Show selected index
    $groups.eq(groupIndex).find(".scroller").slideDown();

I can’t change the first line $groups because this is used further down my function and needs to select all of the groups.

Answer 1

Depending on your HTML, you probably want

$groups.not(":eq("+groupIndex+")").find(".scroller").hide();

If you don’t want to build a selector, you can use filter :

$groups.filter(function(i){return i!=groupIndex}).find(".scroller").hide();