typescript-advanced-types

Define an event map interface mapping event names to payload types, then use a generic class constrained to that map with mapped types for listener storage. The on and emit methods use keyof generics so each event only accepts its declared payload type.

Use conditional types with the infer keyword: T extends (...args: infer P) => infer R captures parameters as P and return type as R. TypeScript also ships built-in ReturnType and Parameters utility types for common cases.

Interfaces are best for object shapes because they produce clearer error messages and support declaration merging. Type aliases are more flexible for unions, conditional types, mapped types, and other computed type expressions.

Yes, strict mode enables strictNullChecks and related flags that make generic constraints and discriminated unions behave correctly. The skill recommends enabling all strict compiler options and preferring unknown over any to preserve type safety.

Each conditional branch forces the compiler to evaluate type relationships recursively, and deeply nested or recursive types multiply that work exponentially. Mitigate by caching computed types in aliases, limiting recursion depth, and simplifying type expressions where possible.

Use type guards with the value is T syntax whenever narrowing unknown or union values at runtime, because they verify the actual value before narrowing. Assertions with as bypass compiler checks and can hide runtime mismatches.