First of all I'm super noob in javascript. But I needed to insert a custom html form in a website with a custom made javascript captcha.

I followed this tutorial here: https://www.makeuseof.com/captcha-validation-html-css-javascript/

Tha captcha shows up correctly but I can submit the form without writing anything in the captcha field. Or if I add the "required" attribute to the captcha input field, I can write anything into it and the form still can be submitted.

How can I make this work? I feel like I'm so close to make this work but I have no idea what's wrong.

Thank you for your help in advance!