lib/collection/item-group.js
function forEachItem (callback) {
        this.items.each(function (item) {
            return ItemGroup.isItemGroup(item) ? item.forEachItem(callback) : callback(item, this);
        }, this);
    }
function forEachItem (callback) {
        this.items.each(function (item) {
            return ItemGroup.isItemGroup(item) ? item.forEachItem(callback) : callback(item, this);
        }, this);
    }
function forEachItem ( callback ) { this . items . each ( function ( item ) { return ItemGroup . isItemGroup ( item ) ? item . forEachItem ( callback ) : callback ( item , this ) ; } , this ) ; }
Calls the callback for each item belonging to itself. If any ItemGroups are encountered,
they will call the callback on their own Items.

@private
@param {Function} callback
Calls the callback for each item belonging to itself . If any ItemGroups are encountered they will call the callback on their own Items .