typescript-advanced-types

Define an event map type mapping event names to payload types, then use generics with mapped types so `on` and `emit` methods infer the correct payload per event. The compiler then rejects mismatched event names or payloads at compile time.

Use conditional types with the `infer` keyword, such as `T extends (...args: infer P) => infer R ? R : never`. TypeScript also ships built-in `ReturnType<T>` and `Parameters<T>` utility types for common cases.

Mapped types iterate over an existing type's keys to transform properties, like making them readonly or optional. Conditional types select a type based on a check using `extends`, enabling logic like extracting types from unions or functions.

Yes, strict mode enables strict null checks and stricter inference, which advanced patterns rely on for correctness. The skill recommends enabling all strict compiler options and preferring `unknown` over `any` to preserve type safety.

Deeply nested or recursive conditional types force the compiler to evaluate many type branches, increasing check time. Mitigate this by caching computed types in aliases, limiting recursion depth, and simplifying type logic where possible.

Use type guards (`value is T`) or assertion functions whenever narrowing unknown or union types at runtime, because they verify the value before narrowing. Type assertions (`as T`) skip checks and can hide runtime errors.