<script>
    $(function () {
        $('.change_button').on("click", function () {
            var data = $(this).data();
            var url = data.href;
            var quantity = $(this).parents('.cart_item').find('.input-num').val();
            var url = url.replace(/\/[0-9]{1,}$/g, '/'+quantity);
            window.location.href = url;
        });
    });
</script>

<input type="text" class="input-num" value="{{ CartItem.quantity }}">
 ...
<a href="java script:void(0);" class="button change_button" data-method="put" data-confirm="false" data-href="{{ url('cart_handle_item', {'operation': 'change', 'productClassId': ProductClass.id, 'quantity' : 1}) }}" {{ csrf_token_for_anchor() }}>更新</a>