Function to add custom mask

/**
 * WordPress Plugin: Masks Form Fields - https://wordpress.org/plugins/masks-form-fields/
 * Function to add custom mask. /wp-content/themes/YOUR-THEME/functions.php
 * Documentation, Demos & Usage Examples - jQuery Mask Plugin v1.14.0 - https://igorescobar.github.io/jQuery-Mask-Plugin/docs.html
 */
function custom_masks_form_fields() {
    ?>
    <script type="text/javascript">
        jQuery(document).ready(function($){
            $("input[name='input_name']").mask('(000) 000-0000');
            // $("input.class_name").mask('custom-mask');
        });
    </script>
    <?php
}

add_action('wp_footer', 'custom_masks_form_fields', 111);