# ipaddr.js — an IPv6 and IPv4 address manipulation library

ipaddr.js is a small (1.9K minified and gzipped) library for manipulating
IP addresses in JavaScript environments. It runs on both CommonJS runtimes
(e.g. [nodejs]) and in a web browser.

ipaddr.js allows you to verify and parse string representation of an IP
address, match it against a CIDR range or range list, determine if it falls
into some reserved ranges (examples include loopback and private ranges),
and convert between IPv4 and IPv4-mapped IPv6 addresses.

[nodejs]: http://nodejs.org

## Installation

`npm install ipaddr.js`

## API

ipaddr.js defines one object in the global scope: `ipaddr`. In CommonJS,
it is exported from the module:

```js
var ipaddr = require('ipaddr.js');
```

The API consists of several global methods and two classes: ipaddr.IPv6 and ipaddr.IPv4.

### Global methods

There are three global methods defined: `ipaddr.isValid`, `ipaddr.parse` and
`ipaddr.process`. All of them receive a string as a single parameter.

The `ipaddr.isValid` method returns `true` if the address is a valid IPv4 or
IPv6 address, and `false` otherwise. It does not throw any exceptions.

The `ipaddr.parse` method returns an object representing the IP address,
or throws an `Error` if the passed string is not a valid representation of an
IP address.

The `ipaddr.process` method works just like the `ipaddr.parse` one, but it
automatically converts IPv4-mapped IPv6 addresses to their IPv4 couterparts
before returning. It is useful when you have a Node.js instance listening
on an IPv6 socket, and the `net.ivp6.bindv6only` sysctl parameter (or its
equivalent on non-Linux OS) is set to 0. In this case, you can accept IPv4
connections on your IPv6-only socket, but the remote address will be mangled.
Use `ipaddr.process` method to automatically demangle it.

### Object representation

Parsing methods return an object which descends from `ipaddr.IPv6` or
`ipaddr.IPv4`. These objects share some properties, but most of them differ.

#### Shared properties

One can determine the type of address by calling `addr.kind()`. It will return
either `"ipv6"` or `"ipv4"`.

An address can be converted back to its string representation with `addr.toString()`.
Note that this method:
 * does not return the original string used to create the object (in fact, there is
   no way of getting that string)
 * returns a compact representation (when it is applicable)

A `match(range, bits)` method can be used to check if the address falls into a
certain CIDR range.
Note that an address can be (obviously) matched only against an address of the same type.

For example:

```js
var addr = ipaddr.parse("2001:db8:1234::1");
var range = ipaddr.parse("2001:db8::");

addr.match(range, 32); // => true
```

A `range()` method returns one of predefined names for several special ranges defined
by IP protocols. The exact names (and their respective CIDR ranges) can be looked up
in the source: [IPv6 ranges] and [IPv4 ranges]. Some common ones include `"unicast"`
(the default one) and `"reserved"`.

You can match against your own range list by using
`ipaddr.subnetMatch(address, rangeList, defaultName)` method. It can work with both
IPv6 and IPv4 addresses, and accepts a name-to-subnet map as the range list. For example:

```js
var rangeList = {
  documentationOnly: [ ipaddr.parse('2001:db8::'), 32 ],
  tunnelProviders: [
    [ ipaddr.parse('2001:470::'), 32 ], // he.net
    [ ipaddr.parse('2001:5c0::'), 32 ]  // freenet6
  ]
};
ipaddr.subnetMatch(ipaddr.parse('2001:470:8:66::1'), rangeList, 'unknown'); // => "he.net"
```

The addresses can be converted to their byte representation with `toByteArray()`.
(Actually, JavaScript mostly does not know about byte buffers. They are emulated with
arrays of numbers, each in range of 0..255.)

```js
var bytes = ipaddr.parse('2a00:1450:8007::68').toByteArray(); // ipv6.google.com
bytes // => [42, 0x00, 0x14, 0x50, 0x80, 0x07, 0x00, <zeroes...>, 0x00, 0x68 ]
```

The `ipaddr.IPv4` and `ipaddr.IPv6` objects have some methods defined, too. All of them
have the same interface for both protocols, and are similar to global methods.

`ipaddr.IPvX.isValid(string)` can be used to check if the string is a valid address
for particular protocol, and `ipaddr.IPvX.parse(string)` is the error-throwing parser.

[IPv6 ranges]: https://github.com/whitequark/ipaddr.js/blob/master/src/ipaddr.coffee#L186
[IPv4 ranges]: https://github.com/whitequark/ipaddr.js/blob/master/src/ipaddr.coffee#L71

#### IPv6 properties

Sometimes you will want to convert IPv6 not to a compact string representation (with
the `::` substitution); the `toNormalizedString()` method will return an address where
all zeroes are explicit.

For example:

```js
var addr = ipaddr.parse("2001:0db8::0001");
addr.toString(); // => "2001:db8::1"
addr.toNormalizedString(); // => "2001:db8:0:0:0:0:0:1"
```

The `isIPv4MappedAddress()` method will return `true` if this address is an IPv4-mapped
one, and `toIPv4Address()` will return an IPv4 object address.

To access the underlying binary representation of the address, use `addr.parts`.

```js
var addr = ipaddr.parse("2001:db8:10::1234:DEAD");
addr.parts // => [0x2001, 0xdb8, 0x10, 0, 0, 0, 0x1234, 0xdead]
```

#### IPv4 properties

`toIPv4MappedAddress()` will return a corresponding IPv4-mapped IPv6 address.

To access the underlying representation of the address, use `addr.octets`.

```js
var addr = ipaddr.parse("192.168.1.1");
addr.octets // => [192, 168, 1, 1]
```
