Ajax request not sent?

Question

JavaScript

Good evening, to the point:
request:

$(document).ready(function () {
        $('.on-tree').click(function () {
            var mySponsorNumber = $(this).attr('id'),
                url = '/all/add_item_tree.php';
            $.ajax({
                type: "POST",
                url: url,
                data: {treeElm: mySponsorNumber},
                dataType: 'json',
                success: function (result) {
                    if (result) {
                        alert('ok');
                        console.log(result);
                    } else {
                        alert('error');
                    }
                },
                error: function () {
                    alert('error2');
                }
            });

        });
    });

file add_item_tree.php

<?php
session_start();
require_once("mysql/db.php");
$itemTree = $_POST['treeElm'];
if($itemTree){
    $out = array(
        'testAjax' => $itemTree
    );
}else{
    $out = array(
        'testAjax' => 'syka blyat'
    );
}
header('Content-Type: text/json; charset=utf-8');

echo json_encode($out);

While looking for errors, I cut the code a lot, when clicked, an error occurs: function () { alert('error2'); }(window)
Thank you!

Answer 1

Obviously a bug on the server. Most likely, not valid JSON is coming, get the response that comes from the server, and check it for validity with any online service