Wordpress wp admin ajax - 有时可行，有时却不行

Question

I'm trying to do some form validation with Wordpress and jQuery Validate plugin. My js code is:

<script type="text/javascript">
    var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";

    // submit reg-form
    jQuery(document).ready(function ($) {
        $.ajaxSetup({
            cache: false
        });

        $("#username").change(function(){
            $("#username").removeData("previousValue");
        });

        $("#moto_register").validate({
            ignore: "",
            rules: {
                username: {
                    remote: {
                        url: ajaxurl,
                        type: "post",
                        data: {
                            username: function() {
                                return $( "#username" ).val();
                            },
                            action: 'moto_validate_username'
                        }
                    }
                },
            },
            submitHandler: function(form) {
                var sData = $(form).serialize();
                $.ajax({
                    url: ajaxurl,
                    async: false,
                    type: 'POST',
                    data: sData,
                    success: function (data) {
                        if (console.log) console.log(data);

                        location.href = "http://test.net/?page_id=30 "
                    }
                });
            }
        });

Im the Wordpress plugin I have following code:

function moto_validate_username() {
$user_id = username_exists( $_POST['username'] );
 if ( !$user_id) echo 'true';
 else echo 'false';
 exit();
}
add_action( 'wp_ajax_nopriv_moto_validate_username', 'moto_validate_username' );
add_action( 'wp_ajax_moto_validate_username', 'moto_validate_username' );

this works SOMETIMES only, and sometimes doesn't. The AJAX seems to be actualy fired, but there's no response, and so no validation. Anyone has an idea why?

Answer 1

The problem seemed to be in removing the pages for non-admin users. When I changed it to:

function moto_remove_menu_pages() {

    global $user_ID;
    if (!$_POST['action'] == 'moto_validate_username') {
        if ( $user_ID != '1' ) {
            remove_menu_page('edit.php'); // Posts
            remove_menu_page('upload.php'); // Media
            remove_menu_page('link-manager.php'); // Links
            remove_menu_page('edit-comments.php'); // Comments
            remove_menu_page('edit.php?post_type=page'); // Pages
            remove_menu_page('plugins.php'); // Plugins
            remove_menu_page('themes.php'); // Appearance
            remove_menu_page('tools.php'); // Tools
            remove_menu_page('options-general.php'); // Settings
            remove_submenu_page( 'index.php', 'update-core.php' );
        }
    }
}
add_action( 'admin_init', 'moto_remove_menu_pages' );

it magically started to work.