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 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` to capture parameters and return types. 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 `Partial` or `Readonly`. Conditional types select a type based on a condition using `extends`, enabling logic like extracting types from unions or functions.

Prefer `interface` for object shapes because it produces clearer error messages and supports declaration merging. Use `type` for unions, tuples, conditional types, and other complex type compositions that interfaces cannot express.

Using `any` disables type checking entirely, defeating TypeScript's compile-time safety and hiding bugs until runtime. Use `unknown` instead, which forces explicit type narrowing through guards before the value can be used.

Deeply nested conditional types and unbounded recursive types slow compilation significantly. Cache complex type computations, limit recursion depth, and prefer simpler type expressions when they achieve the same safety guarantees.