How can websites defend against JavaScript-based DDoS attacks?

Websites can defend against JavaScript-based DDoS attacks through various measures. These include implementing robust Web Application Firewalls (WAFs) that can detect and block malicious traffic patterns, rate limiting requests from individual IPs, using Content Delivery Networks (CDNs) to distribute traffic and absorb attacks, and employing CAPTCHAs or other challenge-response mechanisms to verify human users.