send the AJAX request

ajax.js

function modular_ajax(url, type, formData) {
    // Most simple modular AJAX building block
    $.ajax({
        url: url,
        type: type,
        data: formData,
        processData: false,
        contentType: false,
        beforeSend: function() {
            // show the preloader (progress bar)
            $('#form-response').html("<div class='progress'><div class='indeterminate'></div></div>");
        },
        complete: function () {
            // hide the preloader (progress bar)
            $('#form-response').html("");
        },
        success: function ( data ){
            if ( !$.trim( data.feedback )) { // response from Flask is empty
                toast_error_msg = "An empty response was returned.";
                toast_category = "danger";
            }
            else { // response from Flask contains elements
                toast_error_msg = data.feedback;
                toast_category = data.category;
            }
        },
        error: function(xhr) {console.log("error. see details below.");
            console.log(xhr.status + ": " + xhr.responseText);
            toast_error_msg = "An error occured";
            toast_category = "danger";
        },
    }).done(function() {
        M.toast({html: toast_error_msg, classes: 'bg-' +toast_category+ ' text-white'});
    });
};

var csrf_token = "{{ csrf_token() }}";

$.ajaxSetup({
    beforeSend: function(xhr, settings) {
        if (!/^(GET|HEAD|OPTIONS|TRACE)$/i.test(settings.type) && !this.crossDomain) {
            xhr.setRequestHeader("X-CSRFToken", csrf_token);
        }
    }
});