Add number conversion utilities (#29)

* Add number conversion utilities

* Update after checks

* Add isNull

docs/README.md

@@ -9,6 +9,7 @@ Utility methods for this package are split into groups
 - [is](is.md) Type checking utilities
 - [jsonrpc](jsonrpc.md) Convenience functions for values from @polkadot/api-jsonrpc
 - [keccak](keccak.md) Create Keccak256 values as hex, string & buffer output
+- [number](number.md) Utility methods to convert to and from `number` values
 - [u8a](u8a.md) Utility methods to convert to and from `Uint8Array` objects
 
 # Available methods

docs/is.md

@@ -8,6 +8,7 @@ Type checking utilities
 - [isFunction](#isfunction) Tests for a `function`.
 - [isHex](#ishex) Tests for a hex string.
 - [isInstanceOf](#isinstanceof) Tests for a instance of a class.
+- [isNull](#isnull) Tests for a `null` values.
 - [isNumber](#isnumber) Tests for a JavaScript number.
 - [isString](#isstring) Tests for a string.
 - [isUint8Array](#isuint8array) Tests for a `Uint8Array` object instance.
@@ -116,6 +117,23 @@ import { isInstanceOf } from '@polkadot/util';
 console.log('isinstanceOf', isInstanceOf(new Array(0), Array)); // => true
 ```
 
+## isNull
+
+Tests for a `null` values.
+
+```js
+isNull (value: any): 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.

docs/number.md

@@ -0,0 +1,76 @@
+# number
+
+Utility methods to convert to and from `number` values 
+
+- [numberFromBuffer](#numberfrombuffer) Creates a Number value from a Buffer object.
+- [numberFromHex](#numberfromhex) Creates a Number value from a Buffer object.
+- [numberToBuffer](#numbertobuffer) Creates a Buffer object from a number.
+- [numberToHex](#numbertohex) Creates a hex value from a number.
+
+## numberFromBuffer
+
+Creates a Number value from a Buffer object.
+
+```js
+numberFromBuffer (value?: Buffer): number
+```
+
+
+`null` inputs returns an NaN result, `Buffer` values return the actual value as a `Number`.
+
+```js
+import { numberFromBuffer } from '@polkadot/util';
+
+numberFromBuffer(Buffer.from([12, 34, 56])); // => 0x123456
+```
+
+## numberFromHex
+
+Creates a Number value from a Buffer object.
+
+```js
+numberFromHex (value?: Hex): number
+```
+
+
+`null` inputs returns an Nan result, `hex` values return the actual value as a `Number`.
+
+```js
+import { numberFromHex } from '@polkadot/util';
+
+numberFromBuffer('0x1234'); // => 0x1234
+```
+
+## numberToBuffer
+
+Creates a Buffer object from a number.
+
+```js
+numberToBuffer (value?: number): Buffer
+```
+
+
+`null`/`undefined`/`NaN` inputs returns an empty `Buffer` result. `number` input values return the actual bytes value converted to a `Buffer`.
+
+```js
+import { numberToBuffer } from '@polkadot/util';
+
+const buffer = numberToBuffer('0x1234'); // => Buffer.from([0x12, 0x34])
+```
+
+## numberToHex
+
+Creates a hex value from a number.
+
+```js
+numberToHex (value?: number): string
+```
+
+
+`null`/`undefined`/`NaN` inputs returns an empty `0x` result. `number` input values return the actual bytes value converted to a `hex`.
+
+```js
+import { numberToHex } from '@polkadot/util';
+
+const hex = numberToHex(0x1234); // => '0x1234'
+```