function lookup
Usage in Deno
```typescript import { lookup } from "node:node__dns--promises.d.ts"; ```
lookup(hostname: string,family: number,): Promise<LookupAddress>
Resolves a host name (e.g. `'nodejs.org'`) into the first found A (IPv4) or
AAAA (IPv6) record. All `option` properties are optional. If `options` is an
integer, then it must be `4` or `6` – if `options` is not provided, then IPv4
and IPv6 addresses are both returned if found.
With the `all` option set to `true`, the `Promise` is resolved with `addresses` being an array of objects with the properties `address` and `family`.
On error, the `Promise` is rejected with an [`Error`](https://nodejs.org/docs/latest-v20.x/api/errors.html#class-error) object, where `err.code` is the error code.
Keep in mind that `err.code` will be set to `'ENOTFOUND'` not only when
the host name does not exist but also when the lookup fails in other ways
such as no available file descriptors.
[`dnsPromises.lookup()`](https://nodejs.org/docs/latest-v20.x/api/dns.html#dnspromiseslookuphostname-options) does not necessarily have anything to do with the DNS
protocol. The implementation uses an operating system facility that can
associate names with addresses and vice versa. This implementation can have
subtle but important consequences on the behavior of any Node.js program. Please
take some time to consult the [Implementation considerations section](https://nodejs.org/docs/latest-v20.x/api/dns.html#implementation-considerations) before
using `dnsPromises.lookup()`.
Example usage:
```js
import dns from 'node:dns';
const dnsPromises = dns.promises;
const options = {
family: 6,
hints: dns.ADDRCONFIG | dns.V4MAPPED,
};
dnsPromises.lookup('example.com', options).then((result) => {
console.log('address: %j family: IPv%s', result.address, result.family);
// address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6
});
// When options.all is true, the result will be an Array.
options.all = true;
dnsPromises.lookup('example.com', options).then((result) => {
console.log('addresses: %j', result);
// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]
});
```
Promise<LookupAddress>
lookup(hostname: string,options: LookupOneOptions,): Promise<LookupAddress>
options: LookupOneOptions
Promise<LookupAddress>
lookup(hostname: string,options: LookupAllOptions,): Promise<LookupAddress[]>
options: LookupAllOptions
Promise<LookupAddress[]>
lookup(hostname: string,options: LookupOptions,): Promise<LookupAddress | LookupAddress[]>
options: LookupOptions
Promise<LookupAddress | LookupAddress[]>
lookup(hostname: string): Promise<LookupAddress>
Promise<LookupAddress>