* `format`: {string} Must be one of `'raw'`, `'pkcs8'`, `'spki'`, `'jwk'`, or

`'node.keyObject'`.

* `key`: {CryptoKey}

* Returns: {Promise} containing {ArrayBuffer}, or, if `format` is

`'node.keyObject'`, a {KeyObject}.

Exports the given key into the specified format, if supported.

* `format`: {string} Must be one of `'raw'`, `'pkcs8'`, `'spki'`, `'jwk'`, or

`'node.keyObject'`.

* `keyData`: {ArrayBuffer|TypedArray|DataView|Buffer|KeyObject}

* `algorithm`: {RsaHashedImportParams|EcKeyImportParams|HmacImportParams|AesImportParams|Pbkdf2ImportParams|NodeDsaImportParams|NodeDhImportParams|NodeScryptImportParams|NodeEdKeyImportParams}

The Node.js Web Crypto API extends various aspects of the Web Crypto API.

These extensions are consistently identified by prepending names with the

`node.` prefix. For instance, the `'node.keyObject'` key format can be

used with the `subtle.exportKey()` and `subtle.importKey()` methods to

convert between a WebCrypto {CryptoKey} object and a Node.js {KeyObject}.