I’d probably fire someone if I started to see `JSON.parse(…)` everywhere in a codebase just for “performance reasons” …
Yep, and I'd fire you for doing that! There are better ways to manage instead of showing off your authority. Oh, and by the way, would some JSON.parse statements for performance be the worst thing in your codebase(s) you guess? I mean, I cannot believe that would be the worse in your codebase. Also, if it really helps to use some JSON.parse for creating big objects for performance reasons, who cares? Instead of firing 'someone' maybe you can add some annotation to it for readability (or if that is below your imaginary level, ask the developer if he/she can add that).
Sry, but I hate people that misuse their authority by imposing their subjective opinions.