Mistakes I Made as a Frontend Engineer (And What They Actually Cost Me)

I've shipped a 2s → 0.2s FCP improvement. I've cut build times from 20 minutes to 90 seconds by making the right framework call. I've led an Angular migration across 500+ components with a 12-engineer team. None of that changes the fact that I made avoidable mistakes early in my career. Some from ignorance, some from arrogance, some from nobody being around to tell me otherwise. This is for junior and mid-level engineers who are still in the window where these mistakes are correctable. 1. I Stayed With jQuery Because It Was Working (2013 - 2015) In college, I built personal projects with jQuery. It worked. I never had a reason to look further. No one around me, faculty included knew much more than that. So I didn't push. That attitude this is enough, I'm getting results — followed me into my first job. When the industry had already moved to Angular and React, I was still thinking in jQuery terms. I had to learn a component-based mental model on the job, under delivery pressure, without