Kakao Entertainment Developer Shares 4 Practical TypeScript Tips

A developer from Kakao Entertainment shared four practical tips for reducing type errors and improving productivity when using TypeScript. The author suggests avoiding the use of the any type and maximizing the benefits of static typing.

Union type instead of enum

Since enum generates an object at compile time and affects runtime, union type is recommended for using type information only. While const enum can eliminate runtime impact, union type is more advantageous in terms of developer productivity because it can be used directly as string literals without imports.

Mapped type instead of index signature

It is safer to use mapped type rather than index signature when restricting the types of object keys. Since mapped type does not allow keys that do not belong to the defined type, missing data can be prevented as compile errors when new items are added to the type.

Replacing external package types

When type inference fails in react-redux's useSelector, etc., it is recommended to directly replace the default type (DefaultRootState) using declare module instead of explicitly specifying types every time or creating custom hooks. This allows maintaining clean code without repetitive type annotations.

Utilizing type guards

Type guards should be actively utilized to narrow down type scopes using typeof, in keywords, and common properties (discriminated unions). Since TypeScript 3.7, conditional type assertions can be performed using the asserts keyword, ensuring both readability and stability.