No captcha?

Hello,
I am learning programming and just discovered this website. But I am curious, how does it protect its users from spammers (people who post illegal or annoying things) without a reCaptcha? I thought clicking this blue box is required to prove that you are not a robot, can you please share any javascript that you use for this purpose?
Thank you and have a nice day,
Brian

There is a nasty fat bearded bum living near Boston. He is known to approach little children, offering to show them his MSwinedows. He doesn't shower and eats toe jam, so kids get scared just by his smell!