Nothing like trying to understand a single 1500-line source file that implements the API usage in the frontend. Without a single comment.
No, wait. There are comments! But it's only commented-out code. Or explicit shit (like "gets the version" before a getAssetVersion function).

Functions with unused parameters? ✅
Weird var names (like "tmpX")? ✅
`console.log(var)` everywhere? ✅
Long-ass lines with 150+ chars? ✅
Duplicate code? ✅✅
Not a single interface was used so everything is var: any? ✅
Random unreadable RegEx? ✅
If-chains of 6+ more levels? ✅
Many `else if` towers instead of a switch? ✅
And did I mention it was written by a fucker who can't speak proper English so shit like visiable, cataloge and isExist is everywhere? Yeah.

Fun day at the office reading spaghetti code 🙃