TypeScript

Superstruct is designed with TypeScript in mind, so that you don't need to duplicate type definitions.

Utilities

Describe

The Describe utility returns a type representing a struct for a given valid value type. This allows you to ensure you're writing your struct definitions properly, for example:

type User = {
  id: number
  name: string
}

const User: Describe<User> = object({
  id: string(), // This mistake will fail to pass type checking!
  name: string(),
})

🤖 There are limitations to what Describe can do, specifically it will always assume object types are as strict as possible. So describing the type() struct is not possible, and simple unions of strings will be required to use enums().

Infer

The Infer utility type extracts the type of a valid value from a struct definition. This allows you to avoid having to duplicate effort when writing typings, for example:

const User = object({
  id: number(),
  name: string(),
})

type User = Infer<typeof User>
// type User = {
//   id: number
//   name: string
// }

🤖 If you are not using TypeScript's strictNullChecks option, Superstruct will be unable to infer your "optional" types correctly and will mark all types as optional.