jQuery script isn't posting to database

This is a jQuery script I'm working on to post inputs to a database, assuming the user submitting the data is logged in, and hasn't made an existing entry for the item the user is submitting data for.

Currently it's not producing any results, and I'm not entirely sure why since I don't work with jQuery that often.

Here is a flow chart illustrating what I'm trying to accomplish:

jQuery(document).ready(function() {
    var data = {
        action: 'is_user_logged_in'
    };
    jQuery.post(ajaxurl, data, function(response) {
            if (response == 'yes') {
                // user is logged in
                jQuery.ajax({
                        type: 'POST',
                        url: MyAjax.ajaxurl,
                        data: {
                            "action": "check_db",
                            "user": user,
                            "ItemID": ItemID
                        },
                        function(data) {
                            if (data.exists) {
                                //existing entry found, update entry
                                function UpdateRecord(id) {
                                    jQuery.ajax({
                                        type: 'POST',
                                        url: MyAjax
                                            .ajaxurl,
                                        data: {
                                            "action": "update_entry",
                                            "ItemID": ItemID,
                                            "Price": Price,
                                            "user": user
                                        },
                                        success: function(
                                            response
                                        ) {
                                            alert
                                                (
                                                    "Price successfully submitted."
                                                );
                                        }
                                    });
                                }
                            } else {
                                //existing entry not found, create new entry
                                jQuery("#submit").click(
                                    function() {
                                        var name = jQuery(
                                            "#ItemID").val();
                                        jQuery.ajax({
                                            type: 'POST',
                                            url: MyAjax
                                                .ajaxurl,
                                            data: {
                                                "action": "post_entry",
                                                "ItemID": ItemID,
                                                "Price": Price,
                                                "user": user
                                            },
                                            success: function(
                                                response
                                            ) {
                                                alert
                                                    (
                                                        "Price successfully submitted."
                                                    );
                                            }
                                        });
                                    });
                            });
                    }
                }, 'JSON');
        } else {
            // user is not logged in
            alert("You must be logged in to submit prices.");
        }
    }
});