JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.3/themes/base/jquery-ui.css">
<form>
    <input type="text" id="addCatalogItem" />
</form>

JavaScript

function updateWeight() {
    var z = $("input.count").length;
    alert(z);
}

$("#addCatalogItem").autocomplete({
    source: ['Somewhere', 'over', 'the'
                        , 'rainbow', 'lies', 'teachers', 'T-shirt', 'television'],
    minLength: 2,
    select: function(event, ui) {

        var q = ui.item.product_id;
        $('#product_id').val(q);

        var r = ui.item.value;
        $('#product').val(r);

        var field = '<label>' + r + '</label><input class=\"count\" type=\"text\" value=\"\" name=\"field[' + q + ']\"/>';

        var $item = $("form");

        $(field).appendTo($item);
        updateWeight();
    }
});