# is

Type checking utilities 

- [isBN](#isbn) Tests for a `BN` object instance.
- [isBoolean](#isboolean) Tests for a boolean value.
- [isBuffer](#isbuffer) Tests for a `Buffer` object instance.
- [isError](#iserror) Tests for a `Error` object instance.
- [isFunction](#isfunction) Tests for a `function`.
- [isHex](#ishex) Tests for a hex string.
- [isInstanceOf](#isinstanceof) Tests for a instance of a class.
- [isIp](#isip) Tests if the value is a valid IP address
- [isNull](#isnull) Tests for a `null` values.
- [isNumber](#isnumber) Tests for a JavaScript number.
- [isObject](#isobject) Tests for an `object`.
- [isString](#isstring) Tests for a string.
- [isUint8Array](#isuint8array) Tests for a `Uint8Array` object instance.
- [isUndefined](#isundefined) Tests for a `undefined` values.

## isBN

Tests for a `BN` object instance. 

```js
isBN (value: mixed): boolean
```


Checks to see if the input object is an instance of `BN` (bn.js).

```js
import BN from 'bn.js';
import { isBN } from '@polkadot/util';

console.log('isBN', isBN(new BN(1))); // => true
```

## isBoolean

Tests for a boolean value. 

```js
isBoolean (value: mixed): boolean
```


Checks to see if the input value is a JavaScript boolean.

```js
import { isBoolean } from '@polkadot/util';

isBoolean(false); // => true
```

## isBuffer

Tests for a `Buffer` object instance. 

```js
isBuffer (value: mixed): boolean
```


Checks to see if the input object is an instance of `Buffer`.

```js
import { isBuffer } from '@polkadot/util';

console.log('isBuffer', isBuffer(Buffer.from([]))); // => true
```

## isError

Tests for a `Error` object instance. 

```js
isError (value: mixed): boolean
```


Checks to see if the input object is an instance of `Error`.

```js
import { isError } from '@polkadot/util';

console.log('isError', isError(new Error('message'))); // => true
```

## isFunction

Tests for a `function`. 

```js
isFunction (value: mixed): boolean
```


Checks to see if the input value is a JavaScript function.

```js
import { isFunction } from '@polkadot/util';

console.log('isFunction', isFunction(() => false)); // => true
```

## isHex

Tests for a hex string. 

```js
isHex (value: string, bitLength: number = -1): boolean
```


Checks to see if the input value is a `0x` prefixed hex string. Optionally (`bitLength` !== -1) checks to see if the bitLength is correct.

```js
import { isHex } from '@polkadot/util';

isHex('0x1234'); // => true
isHex('0x1234', 8); // => false
```

## isInstanceOf

Tests for a instance of a class. 

```js
isInstanceOf (value: mixed, clazz: Class<mixed>): boolean
```


Checks to see if the input value is an instance of the test class.

```js
import { isInstanceOf } from '@polkadot/util';

console.log('isInstanceOf', isInstanceOf(new Array(0), Array)); // => true
```

## isIp

Tests if the value is a valid IP address 

```js
isIp (value: string, type?: 'v4' | 'v6'): boolean
```


Checks to see if the value is a valid IP address. Optionally check for either v4/v6

```js
import { isIp } from '@polkadot/util';

isIp('192.168.0.1')); // => true
isIp('1:2:3:4:5:6:7:8'); // => true
isIp('192.168.0.1', 'v6')); // => false
isIp('1:2:3:4:5:6:7:8', 'v4'); // => false
```

## isNull

Tests for a `null` values. 

```js
isNull (value: mixed): boolean
```


Checks to see if the input value is `null`.

```js
import { isNull } from '@polkadot/util';

console.log('isNull', isNull(null)); // => true
```

## isNumber

Tests for a JavaScript number. 

```js
isNumber (value: mixed): boolean
```


Checks to see if the input value is a valid number.

```js
import { isNumber } from '@polkadot/util';

console.log('isNumber', isNumber(1234)); // => true
```

## isObject

Tests for an `object`. 

```js
isObject (value: mixed): boolean
```


Checks to see if the input value is a JavaScript object.

```js
import { isObject } from '@polkadot/util';

isObject({}); // => true
isObject('something'); // => false
```

## isString

Tests for a string. 

```js
isString (value: mixed): boolean
```


Checks to see if the input value is a JavaScript string.

```js
import { isString } from '@polkadot/util';

console.log('isString', isString('test')); // => true
```

## isUint8Array

Tests for a `Uint8Array` object instance. 

```js
isUint8Array (value: mixed): boolean
```


Checks to see if the input object is an instance of `Uint8Array`.

```js
import { isUint8Array } from '@polkadot/util';

console.log('isUint8Array', isUint8Array([])); // => false
```

## isUndefined

Tests for a `undefined` values. 

```js
isUndefined (value: mixed): boolean
```


Checks to see if the input value is `undefined`.

```js
import { isUndefined } from '@polkadot/util';

console.log('isUndefined', isUndefined(void(0))); // => true
```