# `is-domain-name`

> Validate Domain Names as outlined by RFC 2181


## Install

```sh
npm install is-domain-name
```

## Usage

Domain names are composed of labels interleaved with a separator (`.`).
Domain as allowed a total length of 255 chars including separators.
Labels should be between 1 and 63 octets.

Labels allows domains to form a hierarchy, with the right most label acting
as the root. The leftmost label is often called the TLD (Top-Level Domain),
the 2nd leftmost informally called the domain and any label to the right of
those called subdomains.

A common domain with only a single label is `localhost`.

This module checks the following:

* The domain is no longer than 255 chars
* The domain is at least 2 chars. Even though `a` is technically allowed, this module does not allow it
* Labels are between 1 and 63 chars
* Labels start and end with alpha-numeric chars, allowing dashes in between
* An optional root dot can be allowed with a flag, eg. `example.com.`

```js
const assert = require('assert')
const isDomainName = require('is-domain-name')

assert.ok(isDomainName('localhost'))
assert.notOk(isDomainName('-.-'))
```

## API

### isDomainName(domainName, rootDot)
#### domainName

Type: `String`

#### rootDot
Type: `Boolean`<br>
Default: `false`

Whether or not to validate for a trailing dot, signifying the root

## Related

* [`is-http-url`](http://github.com/emilbayes/is-http-url)

## License

[ISC](LICENSE.md)