wp_enqueue_scripts “undefined constant” error

I’m a newbie learning to develop child themes based on a since-retired Treehouse course. I’m building a wedding site on localhost & created a wrapper in app.js, then created header.php & footer.php, and added dummy text between get_header(); & get_footer() in index.php.

Refreshing the page to see the results, I got this error message: “Warning: Use of undefined constant wp_enqueue_scripts – assumed ‘wp_enqueue_scripts’ (this will throw an Error in a future version of PHP) in /srv/www/theknowithalls/public_html/wp-content/themes/suki_wedding/functions.php on line 34

Warning: Use of undefined constant wp_theme_js – assumed ‘wp_theme_js’ (this will throw an Error in a future version of PHP) in /srv/www/theknowithalls/public_html/wp-content/themes/suki_wedding/functions.php on line 34

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘wp_theme_js’ not found or invalid function name in /srv/www/theknowithalls/public_html/wp-includes/class-wp-hook.php on line 286”

(The dummy text appeared, btw.)

Not sure what the above means. Please advise.

Thanks.