WPForms - Populate a field from another field on same form

wpf-populate-fields-same-form.php

<?php
/**
 * Populate a field from another field on same form
 *
 * @link https://wpforms.com/developers/how-to-pre-populate-fields-in-the-same-form/
 */

add_action( 'wpforms_wp_footer_end',  function() {
    ?>
    <script>
        jQuery(function($){
 
            var formID = 22397; // Change form ID
            var faxNumber = 7; // Fax number field ID to grab value 
            var faxEmail = 8; // Fax email field ID to pass value to
 
            $( '#wpforms-' + formID + '-field_' + faxNumber ).on( 'change', function() {
                $( '#wpforms-' + formID + '-field_' + faxEmail ).val($(this).val().concat("concatenate some text here"));
            });
 
        });
    </script>
    <?php
}, 10 );