Selection in dhtmlxFolders behaves in same way as in desktop applications:

1. Single click on item selects it;
2. If you click on item when other item(s) selected:

• Holding Shift key - selects all items starting from already selected to currently clicked one;
• Holding Ctrl key - adds currently clicked item to selected items (if this item wasn't selected), removes currently clicked item from selected items (if item was already selected).

To select item with script call the following command:

  selectItem(itemId,ctrl-key-state,shift-key-state);