Dependecy error Magento 2 ('sectionLoadUrl' error)

You should use define in your jquery.cartAjax.js file instead of require, also pass $ as an argument so you can use it in the ajax call, require is specifically designed for phtml files and define for javascript files.

define([
       'jquery',
       'Magento_Checkout/js/action/get-totals'
       ], function ($, getTotalsAction) {

$(document).ready(function(){
    $(".cart-container .form-cart .action.update").remove();
    // On change handler
    jQuery(document).on('change', 'input[name$="[qty]"]', function(){
                console.log("quantity changed");
                var form = jQuery(jQuery(this).closest('form'));

                $.ajax({
                    url: form.attr('action'),
                    data: form.serialize(),
                    showLoader: true,
                    context: this.changedInput,
                    success: function (res) {
                        var parsedResponse = $.parseHTML(res);
                        var result = $(parsedResponse).find("#form-validate");
                        $("#form-validate").replaceWith(result);
                        var deferred = $.Deferred();
                        getTotalsAction([], deferred);
                        console.log('Ajax succes function completed');
                    },
                    error: function (xhr, status, error) {
                        var err = eval("(" + xhr.responseText + ")");
                        console.log(err.Message);
                    }
                });

            }
        );
    });
});

hope it helpes

Update:

i think there's also somehting going wrong with the call to the file

it should look somehting like this: <script>require(['ajaxQty']);</script> where ajaxQty is the name declared in the require-config.js

Okay, I fixed it eventually, with help and thinking of Pascal Wientjes

So, when discussing about what the issue could be with said person, we came to the conclusion that customer-data.js was loaded after cartAjaxQty.js.

Even though I included the Magento_Customer module in a sequence-tag within the module.xml, still customer-data.js still got loaded AFTER my script. I posted a question about this:

<sequence> not working?

Where other people reacted, and so Magento loads customer-data.js via it's layout. So I had to figure out another way. Pascal told maybe you could use a $(document).ready, so I tried but no luck. I thought.

This eventually fixed it: $(window).on("load", function ()

My script.phtml eventually looks like this!

<script>
require ([
        'jquery'
    ],
function ($) {
    $(window).on("load", function () {
        require([
            'Vendor_AjaxCart/js/cartAjaxQty'
        ]);
    });
});

And now all loads fine. It's not the fix I had hoped for, a more cleaner approach would've been my preference but it fixes my error.