reCAPTCHA
Add reCAPTCHA to NodeJS and ExpressJS app with AJAX form
Google's reCAPTCHA is great for getting rid of those pesky bots spamming your contact forms. Implementing reCAPTCHA on your site is very easy, albeit somewhat confusing if you try to follow official documentation. Below example assumes you're using NodeJS with ExpressJS for back-end and Pug