typescript-pro

Generics parameterize functions and classes with type variables, while conditional types select types based on assignability checks using the extends keyword. Combine them with mapped types and infer to build reusable utility types that preserve type safety across abstractions.

Enable strict mode in tsconfig.json, which activates strictNullChecks, noImplicitAny, strictFunctionTypes, and related flags. Add incremental compilation and appropriate target/module settings to balance safety with build performance.

Yes, strict mode integrates with React, Node.js, and Express through typed props, request/response generics, and declaration files. Framework-specific type packages like @types/express provide the base contracts you extend with your own interfaces.

Prefer inference when the compiler can unambiguously determine types, such as initialized variables and return values of well-typed functions. Use explicit annotations for public API boundaries, function parameters, and cases where inference widens types unexpectedly.

Deeply nested conditional types can slow compilation and produce cryptic error messages. Types exist only at compile time, so runtime validation with libraries or manual guards is still required for external data.