Quickstart Jquery插件在网站上显示错误？

I use joomla 3.6 and i installed some plugins, but i'm struggling with this one jquery plugin. In the console it shows me this error

TypeError: $(...).ready is not a function: Anonymous

For the jquery version you need 1.6.1 and for the jquery-UI 1.8.14. But i tested it with the default joomla jquery versions: 1.11.2 and the jquery-UI 1.9.2 on a clear website and it works. So there is no problem with the jquery version.

// Use the .autocomplete() method to compile the list based on input from user
$('#itemCode').autocomplete({
    source: '/db/item-data.php',
    minLength: 1,
    select: function(event, ui) {

I already added the needed scripts in the head.php in joomla templates.

If i remove the no conflict:

/media/jui/js/jquery-noconflict.js

jQuery.noConflict();

Then the plugin is working, but why do i need to remove, maybe, the most important code to let the plugin work?