What are union and intersection types in TypeScript?

Related TypeScript interview questions

• What are generics in TypeScript?

  Generics are type parameters: they let a function, class or type work with many types while keeping the relationship between inputs and outputs, instead of falling back to any.

• What are utility types in TypeScript like Partial, Pick and Omit?

  Utility types are built-in helpers that transform an existing type: Partial makes every field optional, Required the opposite, Pick keeps a set of keys, Omit removes them, and Record builds a key/value map.

• What is the difference between any, unknown and never in TypeScript?

  any turns off checking. unknown is a type-safe any: you must narrow it before use. never means a value cannot exist, used for exhaustive checks and functions that always throw.

• What is type narrowing in TypeScript?

  Narrowing is when TypeScript shrinks a wide type (such as a union) to a more specific type after a runtime check like typeof, instanceof, in, or a custom type guard.