How to Filter multiple Posts in WordPress by tag Using AJAX, without using any plugin

Step-1:
Html Checkbox Like this:

<div>



<p>display all tabs or subjects container:<br>
</p>

<pre class="brush:php;toolbar:false"><!-- Container to display worksheets -->
<div>



<p><strong>Step-2:</strong><br>
create js file:<br>
</p>

<pre class="brush:php;toolbar:false">jQuery(document).ready(function ($) {
    // Fetch Subjects on any checkbox change
    $('.subject-filter').on('change', function () {
        // Gather all selected grades
        var taxonomy = $(this).data('taxonomy'); // Taxonomy name
        var terms = []; // Array to hold selected terms
        $('.subject-filter:checked').each(function () {
            terms.push($(this).val());
        });

        // Fetch Subjects for selected grades
        fetchSubjects(taxonomy, terms);
    });

    // Function to fetch Subjects
    function fetchSubjects(taxonomy = '', terms = []) {
        $.ajax({
            url: ajax_object.ajax_url,
            type: 'POST',
            data: {
                action: 'fetch_subjects',
                nonce: ajax_object.nonce,
                taxonomy: taxonomy,
                terms: terms, // Send array of selected terms
            },
            beforeSend: function () {
                $('.worksheet-container').html('<p>Loading...</p>');
            },
            success: function (response) {
                if (response.success) {
                    $('.worksheet-container').html(response.data.html);
                } else {
                    $('.worksheet-container').html('<p>' + response.data.message + '</p>');
                }
            },
            error: function () {
                $('.worksheet-container').html('<p>An error occurred. Please try again.</p>');
            },
        });
    }
});

Step-3:
Create Functions in functions.php:

// Register AJAX action for logged-in users (you can add for non-logged-in users too)
add_action('wp_ajax_fetch_subjects', 'fetch_subjects');
add_action('wp_ajax_nopriv_fetch_subjects', 'fetch_subjects');
function fetch_subjects() {
    // Verify nonce for security
    if (!isset($_POST['nonce']) || !wp_verify_nonce($_POST['nonce'], 'ajax_nonce')) {
        wp_send_json_error(array('message' => 'Nonce verification failed.'));
        wp_die();
    }

    // Get taxonomy and terms from the AJAX request
    $taxonomy = isset($_POST['taxonomy']) ? sanitize_text_field($_POST['taxonomy']) : '';
    $terms = isset($_POST['terms']) ? array_map('sanitize_text_field', $_POST['terms']) : array();

    // Default query arguments
    $args = array(
        'post_type'      => 'worksheet',
        'posts_per_page' => -1, // Fetch all posts
    );

    // If terms are selected, modify the query
    if (!empty($taxonomy) && !empty($terms)) {
        $args['tax_query'] = array(
            array(
                'taxonomy' => $taxonomy,
                'field'    => 'slug',
                'terms'    => $terms, // Pass the array of selected terms
                'operator' => 'IN',   // Match any of the selected terms
            ),
        );
    }

    // Run WP_Query to fetch posts
    $query = new WP_Query($args);

    // Check if any posts were found
    if ($query->have_posts()) {
        $html = '';
        while ($query->have_posts()) {
            $query->the_post();
            // Output the post HTML
            $html .= '<div>




          </div>