function lookup
Usage in Deno
```typescript import { lookup } from "node:node__dns.d.ts"; ```
lookup(hostname: string,family: number,callback: (err: ErrnoException | null,address: string,family: number,) => void,): void
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 `0` or not provided, then
IPv4 and IPv6 addresses are both returned if found.
With the `all` option set to `true`, the arguments for `callback` change to `(err, addresses)`, with `addresses` being an array of objects with the
properties `address` and `family`.
On error, `err` is an `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.
`dns.lookup()` 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-v22.x/api/dns.html#implementation-considerations)
before using `dns.lookup()`.
Example usage:
```js
import dns from 'node:dns';
const options = {
family: 6,
hints: dns.ADDRCONFIG | dns.V4MAPPED,
};
dns.lookup('example.com', options, (err, address, family) =>
console.log('address: %j family: IPv%s', address, 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;
dns.lookup('example.com', options, (err, addresses) =>
console.log('addresses: %j', addresses));
// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]
```
If this method is invoked as its [util.promisify()](https://nodejs.org/docs/latest-v22.x/api/util.html#utilpromisifyoriginal) ed
version, and `all` is not set to `true`, it returns a `Promise` for an `Object` with `address` and `family` properties.
void
lookup(hostname: string,options: LookupOneOptions,callback: (err: ErrnoException | null,address: string,family: number,) => void,): void
options: LookupOneOptions
void
lookup(hostname: string,options: LookupAllOptions,callback: (err: ErrnoException | null,addresses: LookupAddress[],) => void,): void
options: LookupAllOptions
callback: (err: ErrnoException | null,addresses: LookupAddress[],) => void
void
lookup(): void
options: LookupOptions
void