@xieyuheng/ty NPM

Ty

Validate untyped data and return well typed result.

This package has no dependencies.

Install

npm i @xieyuheng/ty

Examples

Validation untyped data

import ty, { Obtain } from "@xieyuheng/ty"

const userSchema = ty.object({
  id: ty.int({ min: 0 }),
  first_name: ty.string(),
  last_name: ty.string(),
})

type User = Obtain<typeof userSchema>

// NOTE We can extract a `User` type from the type of `userSchema`,
//   which will be the same as the following type definition:

// type User = {
//   id: number
//   first_name: string
//   last_name: string
// }

{
  const data: any = {
    id: 1,
    first_name: "Yuheng",
    last_name: "Xie",
  }

  const user: User = userSchema.validate(data)
}

Recursive and generic schema

type List<T> = null | { head: T; tail: List<T> }

function cons<T>(head: T, tail: List<T>): List<T> {
  return { head, tail }
}

function listSchema<T>(itemSchema: Schema<T>): Schema<List<T>> {
  const nullSchema = ty.null()
  const consSchema = ty.object({
    head: itemSchema,
    tail: ty.lazy(() => listSchema(itemSchema)),
  })
  return ty.union(nullSchema, consSchema)
}

{
  const schema = listSchema(ty.string())
  const data0: List<string> = schema.validate(null)
  const data1: List<string> = schema.validate(cons("a", null))
  const data2: List<string> = schema.validate(cons("a", cons("b", null)))
  const data3: List<string> = schema.validate(
    cons("a", cons("b", cons("c", null))),
  )
  schema.expectInvalid(cons(1, null))
  schema.expectInvalid(cons(1, cons(2, null)))
  schema.expectInvalid(cons(1, cons(2, cons(3, null))))
}

{
  const schema = listSchema(ty.number())
  const data0: List<number> = schema.validate(null)
  const data1: List<number> = schema.validate(cons(1, null))
  const data2: List<number> = schema.validate(cons(1, cons(2, null)))
  const data3: List<number> = schema.validate(cons(1, cons(2, cons(3, null))))
  schema.expectInvalid(cons("a", null))
  schema.expectInvalid(cons("a", cons("b", null)))
  schema.expectInvalid(cons("a", cons("b", cons("c", null))))
}