Debugging legacy code feels like spelunking in a cave without a map, but AI just handed me a high-powered headlamp. We've all been there: staring at a decades-old codebase, wondering if the original developer was a wizard or just really liked semicolons. This isn't about AI writing the code for you, but about it becoming the ultimate rubber duck debugging companion, only this duck actually understands JavaScript. Recently, I got pulled into a project with a monolithic backend written in what felt like JavaScript's forgotten cousin. The kind of code where a single function sprawls across hundreds of lines, variable names like flibbleWibble are common, and the logic defies gravity. There was no documentation, and the original developer's coffee habits were probably the only comments left. My first instinct was to burn it all down and start fresh. My second, thankfully, was to try an AI. I started by feeding it chunks of code, not expecting miracles, but hoping for a starting point.…