Gravity Forms: Make Gravity Form Field Read Only (first page of multi-page or a single page)

functions.php

add_filter( 'gform_pre_render_20', 'webendev_add_readonly_script' );
/**
 * Make Gravity Form Field Read Only (first page of multi-page or a single page)
 *
 */
function webendev_add_readonly_script($form){
    ?>

    <script type="text/javascript">
        jQuery(document).ready(function(){

            jQuery("li.gfield.readonly input").attr("readonly","readonly");
            jQuery("li.gfield.gf_readonly textarea").attr("readonly","readonly");
        });
    </script>

    <?php
    return $form;
}