Can WordPress make an Ajax call that returns the whole HTML page?

Finally got this working after about a week of trying!!

Here is my AJAX Function inside js/script.js

 $.ajax({
            type: 'post',
            //dataType: 'json',
            url: map_ajax_obj.ajaxurl,
            data: {action: 'marker_in_viewport', resultsArray: data, nonce: map_ajax_obj.nonce},
            success: function(result) {
                //console.log(result);
                $('#map-results').html(result);
            },
            error: function(result) {
                console.warn(result);
            }
        });

Inside my functions.php file I have enqueued and localised my wp-admin.php like this

    function load_req_scripts()
    {
        wp_register_script( 'custom-js-script', get_template_directory_uri() . '/js/script.js', array( 'jquery'), '', true);
        wp_enqueue_script( 'custom-js-script' );
    
        wp_localize_script(
            'custom-js-script', //I think this is a dependancy on the above script though not entirely sure
            'map_ajax_obj',
            array (
               
                'ajaxurl' => admin_url('admin-ajax.php'), 
                'nonce'  => wp_create_nonce('ajax_nonce')
            )
        );
    }
    add_action( 'wp_enqueue_scripts', 'load_req_scripts' );

require_once('ajax/accommodation-ajax.php'); //where to handle and return the data to the ajax call

here is the function in my accommodation-ajax.php file

<?php

function marker_in_viewport() {

    $locationResults = $_POST['resultsArray'];

    if (!empty($locationResults)) {

    $posts = get_posts(array(
        'post_type' => 'accommodation',
        'post__in'  => $locationResults    
    ));

    if( $posts ) {  
        
        foreach( $posts as $post ) {

        $id        = $post->ID;
        $title     = get_the_title($id);
        $location  = get_field('location', $id);
        $permalink = get_permalink( $id );
        $gallery   = get_field('gallery', $id);
        $rooms_available_from = get_field('rooms_available_from', $id);
        ?>
        <div class="col-md-4 accom-results-cont pb-3">
            <a href="<?php echo $permalink; ?>" title="Learn more about <?php echo $title; ?>">
                <?php if ( $gallery ) : ?>
                    <div class="accom-results-img-cont">
                        <img class="img-fluid" src="<?php echo $gallery['url']; ?>" alt="An image of <?php echo $title; ?>" >
                    </div>
                <?php endif; ?>
                <div class="accom-results-data-cont pr-3 pt-3">
                    <?php if ( $title ) : ?>
                        <p class="results-title"><b><?php echo $title; ?></b></p>
                    <?php endif; ?>
                </div>
            </a>
        </div>
    <?php } //end for each 
    
    } //end if posts

    } //end if not empty

    else {

        echo "No results found please search again!";

    }

    wp_die();
}

add_action( 'wp_ajax_nopriv_marker_in_viewport', 'marker_in_viewport');
add_action( 'wp_ajax_marker_in_viewport', 'marker_in_viewport');

As to why this now works compared to what I posted above I have no idea!! Could it be the NONCE? though I'm not using it to authenticate in the PHP function. Anyway hope this helps someone or my future self next time I'm banging my head against the wall with wordpress ajax calls.

UPDATE So this stopped working for me again then I realised that it was working when logged in as admin and not workign for logged out and all other users. Because this is a membership site I wanted to block anyone that wasn't an admin form the admin area. Didn't realise that this function was also blocking access to the admin-ajax.php file too. This was redirecting to the Homepage hence why the AJAX call was returning the entire page HTML.

SO I needed to update my function to include:

&& ( ! defined( 'DOING_AJAX' ) || ! DOING_AJAX )

to the following:

//block users from admin if not admin
function blockusers_wps_init() {
        if ( is_admin() && ! current_user_can( 'administrator' ) && ( ! defined( 'DOING_AJAX' ) || ! DOING_AJAX ) ) {
                wp_redirect( home_url() );
                exit;
        }
}

add_action( 'init', 'blockusers_wps_init' );