# Keywords

### TypeScript

<div>All\* built-in TypeScript keywords are directly available.</div>

**string**
```ts
const Keywords = type({
	string: "string",
	date: "Date"
})
```

**fluent**

```ts
const Keywords = type({
	string: type.string,
	date: type.Date
})
```

Common keywords are exposed directly on `type`.

<sup>
	\* `any` and `void` are misleading and unnecessary for runtime validation and
	so are not included as keywords by default.
</sup>

### Subtype

Subtype keywords refine or transform their root type.

**string**
```ts
const Keywords = type({
	dateFormattedString: "string.date",
	transformStringToDate: "string.date.parse",
	isoFormattedString: "string.date.iso",
	transformIsoFormattedStringToDate: "string.date.iso.parse"
})
```

You can easily explore available subtypes via autocomplete by with a partial definition like `"string."`.

**fluent**

```ts
const Keywords = type({
	dateFormattedString: type.keywords.string.date.root,
	isoFormattedString: type.keywords.string.date.iso.root,
	transformStringToDate: type.keywords.string.date.parse,
	transformIsoFormattedStringToDate: type.keywords.string.date.iso.parse
})
```

All built-in keywords and modules are available in `type.keywords`.

`.root` gets the base type of a subtyped module so that it can be used as a `Type` directly.

### All Keywords

This table includes all keywords available in default `type` API. To define your own string-embeddable keywords, see [scopes](https://arktype.io/docs/scopes).

## string

| Alias | Description |
| --- | --- |
| `string` | a string |
| `string.alpha` | only letters |
| `string.alphanumeric` | only letters and digits 0-9 |
| `string.base58` | base58-encoded |
| `string.base64` | base64-encoded |
| `string.base64.url` | base64url-encoded |
| `string.capitalize` | a morph from a string to capitalized |
| `string.capitalize.preformatted` | capitalized |
| `string.creditCard` | a credit card number and a credit card number |
| `string.date` | a string and a parsable date |
| `string.date.epoch` | an integer string representing a safe Unix timestamp |
| `string.date.epoch.parse` | a morph from an integer string representing a safe Unix timestamp to a Date |
| `string.date.iso` | an ISO 8601 (YYYY-MM-DDTHH:mm:ss.sssZ) date |
| `string.date.iso.parse` | a morph from an ISO 8601 (YYYY-MM-DDTHH:mm:ss.sssZ) date to a Date |
| `string.date.parse` | a morph from a string and a parsable date to a Date |
| `string.digits` | only digits 0-9 |
| `string.email` | an email address |
| `string.hex` | hex characters only |
| `string.integer` | a well-formed integer string |
| `string.integer.parse` | a morph from a well-formed integer string to an integer |
| `string.ip` | an IP address |
| `string.ip.v4` | an IPv4 address |
| `string.ip.v6` | an IPv6 address |
| `string.json` | a JSON string |
| `string.json.parse` | safe JSON string parser |
| `string.lower` | a morph from a string to only lowercase letters |
| `string.lower.preformatted` | only lowercase letters |
| `string.normalize` | a morph from a string to NFC-normalized unicode |
| `string.normalize.NFC` | a morph from a string to NFC-normalized unicode |
| `string.normalize.NFC.preformatted` | NFC-normalized unicode |
| `string.normalize.NFD` | a morph from a string to NFD-normalized unicode |
| `string.normalize.NFD.preformatted` | NFD-normalized unicode |
| `string.normalize.NFKC` | a morph from a string to NFKC-normalized unicode |
| `string.normalize.NFKC.preformatted` | NFKC-normalized unicode |
| `string.normalize.NFKD` | a morph from a string to NFKD-normalized unicode |
| `string.normalize.NFKD.preformatted` | NFKD-normalized unicode |
| `string.numeric` | a well-formed numeric string |
| `string.numeric.parse` | a morph from a well-formed numeric string to a number |
| `string.regex` | a string and a regex pattern |
| `string.semver` | a semantic version (see https://semver.org/) |
| `string.trim` | a morph from a string to trimmed |
| `string.trim.preformatted` | trimmed |
| `string.upper` | a morph from a string to only uppercase letters |
| `string.upper.preformatted` | only uppercase letters |
| `string.url` | a string and a URL string |
| `string.url.parse` | a morph from a string and a URL string to a URL instance |
| `string.uuid` | a UUID |
| `string.uuid.v1` | a UUIDv1 |
| `string.uuid.v2` | a UUIDv2 |
| `string.uuid.v3` | a UUIDv3 |
| `string.uuid.v4` | a UUIDv4 |
| `string.uuid.v5` | a UUIDv5 |
| `string.uuid.v6` | a UUIDv6 |
| `string.uuid.v7` | a UUIDv7 |
| `string.uuid.v8` | a UUIDv8 |

## number

| Alias | Description |
| --- | --- |
| `number` | a number |
| `number.Infinity` | Infinity |
| `number.NaN` | NaN |
| `number.NegativeInfinity` | -Infinity |
| `number.epoch` | an integer representing a safe Unix timestamp |
| `number.integer` | an integer |
| `number.safe` | at least -9007199254740991 and at most 9007199254740991 |

## other

| Alias | Description |
| --- | --- |
| `Key` | a string or a symbol |
| `bigint` | a bigint |
| `boolean` | boolean |
| `false` | false |
| `never` | never |
| `null` | null |
| `symbol` | a symbol |
| `true` | true |
| `undefined` | undefined |
| `unknown` | unknown |
| `unknown.any` | unknown |

## object

| Alias | Description |
| --- | --- |
| `object` | an object |
| `object.json` | { [string]: $jsonObject, a number, a string, false, null or true } |
| `object.json.stringify` | a morph from { [string]: $jsonObject, a number, a string, false, null or true } to a string |

## array

| Alias | Description |
| --- | --- |
| `Array` | an array |
| `Array.index` | matched by ^(?:0\|[1-9]\d*)$ |
| `Array.liftFrom` | a generic type for Function |
| `Array.readonly` | an array |
| `ArrayBuffer` | an ArrayBuffer instance |

## FormData

| Alias | Description |
| --- | --- |
| `FormData` | a FormData instance |
| `FormData.parse` | a morph from a FormData instance to an object representing parsed form data |
| `FormData.parsed` | an object representing parsed form data |
| `FormData.value` | a string or a File instance |

## TypedArray

| Alias | Description |
| --- | --- |
| `TypedArray.BigInt64` | a BigInt64Array |
| `TypedArray.BigUint64` | a BigUint64Array |
| `TypedArray.Float32` | a Float32Array |
| `TypedArray.Float64` | a Float64Array |
| `TypedArray.Int16` | an Int16Array |
| `TypedArray.Int32` | an Int32Array |
| `TypedArray.Int8` | an Int8Array |
| `TypedArray.Uint16` | a Uint16Array |
| `TypedArray.Uint32` | a Uint32Array |
| `TypedArray.Uint8` | a Uint8Array |
| `TypedArray.Uint8Clamped` | a Uint8ClampedArray |

## instanceof

| Alias | Description |
| --- | --- |
| `Blob` | a Blob instance |
| `Date` | a Date |
| `Error` | an Error |
| `File` | a File instance |
| `Function` | a function |
| `Headers` | a Headers instance |
| `Map` | a Map |
| `Promise` | a Promise |
| `RegExp` | a RegExp |
| `Request` | a Request instance |
| `Response` | a Response instance |
| `Set` | a Set |
| `URL` | a URL instance |
| `WeakMap` | a WeakMap |
| `WeakSet` | a WeakSet |

## generic

| Alias | Description |
| --- | --- |
| `Exclude` | exclude branches of a union like `Exclude("boolean", "true")` |
| `Extract` | extract branches of a union like `Extract("0 \| false \| 1", "number")` |
| `Merge` | merge an object's properties onto another like `Merge(User, { isAdmin: "true" })` |
| `Omit` | omit a set of properties from an object like `Omit(User, "age")` |
| `Partial` | make all named properties of an object optional like `Partial(User)` |
| `Pick` | pick a set of properties from an object like `Pick(User, "name \| age")` |
| `Record` | instantiate an object from an index signature and corresponding value type like `Record("string", "number")` |
| `Required` | make all named properties of an object required like `Required(User)` |