ArkType Documentation

ArkType provides access to its internal type representation through the .internal property on each Type. This representation is defined in @ark/schema and consists of a tree of nodes. Each node has a kind property that describes its purpose and structure.

Note: APIs under .internal are not officially frozen and are not guaranteed to be semver-stable, though they are considered stable enough for direct access to introspection capabilities.

The extension provides two primary developer experience enhancements:

1. Syntax Highlighting: Provides specialized syntax highlighting for strings that are part of an ArkType definition.
2. Inline Error Summaries: Provides inline type error summaries optimized for ArkType, specifically designed to work with the ErrorLens extension.

ArkType allows you to use built-in TypeScript keywords directly within your type definitions. You can use the string syntax or the fluent API. Note that any and void are not included as keywords by default as they are considered unnecessary for runtime validation.

// Using string syntax
const Keywords = type({
	string: "string",
	date: "Date"
})

// Using fluent API
const Keywords = type({
	string: type.string,
	date: type.Date
})

oRPC has built-in support for the Standard Schema API, meaning ArkType works out of the box for defining input schemas.

import { type } from "arktype"

os.input(
	type({
		name: "string",
		"age?": "number"
	})
)

Ensure your environment meets the following requirements for ArkType:

• TypeScript: version >=5.1.
• Module System: A package.json with "type": "module" (or an environment that supports ESM imports).
• tsconfig.json Configuration:
  • strict or strictNullChecks (required)
  • skipLibCheck (strongly recommended)
  • exactOptionalPropertyTypes (recommended)

ArkType can be used as the input validator in tRPC. The implementation depends on your tRPC version:

• tRPC >= 11: Pass the ArkType Type instance directly to .input().
• tRPC < 11: Pass the .assert property of the ArkType Type instance to .input().

// tRPC >= 11
t.procedure.input(
	type({
		name: "string",
		"age?": "number"
	})
)

// tRPC < 11
t.procedure.input(
	type({
		name: "string",
		"age?": "number"
	}).assert
)

Use the type function from arktype to define a schema using a syntax that closely resembles TypeScript. You can define objects, primitive types, unions, and optional properties (using the ? suffix). To extract the TypeScript type from an ArkType definition for use in your code, use typeof YourType.infer.

import { type } from "arktype"

const User = type({
	name: "string",
	platform: "'android' | 'ios'",
	"versions?": "(number | string)[]"
})

// extract the type if needed
type User = typeof User.infer