TypeScript style

Prerequisite: load the javascript skill first. Every rule in javascript (early returns over else, const over let, no chained ternaries, brace all control-flow bodies, no .forEach) applies to TypeScript too. This skill only adds the TS-specific rules layered on top — types, generics, enums, narrowing.

Personal TS-specific style rules to follow whenever touching TypeScript. Two themes underlie everything:

1. Don't lie to the compiler. Casts, any, !, and @ts-ignore all silently disable type checking. If you're wrong, nothing tells you — until production. Prefer constructs that prove the claim (type guards, satisfies, narrowing).
2. Let the type system do the work. Generics, overloads, utility types, and discriminated unions let TypeScript infer the exact shape at every call site. Stop hand-typing what the compiler can derive.

Both themes catch real bugs that show up when code is refactored or reused — exactly the situations where untyped escape hatches rot fastest.

Part 1 — Don't lie to the compiler

1.1 No as casting — use type guards

as X and especially as unknown as X silently tell the compiler "trust me." A type guard does the same narrowing work and checks reality at runtime, so the call site is honest about what it actually knows.