Add standard and 'double alternate' methods

README.md

@@ -1,2 +1,64 @@
 # uk-modulus-checking
-UK modulus checking.
+Modulus checking allows payment originators to confirm that customer codes and account numbers are compatible before submitting a Bacs Direct Credit of Direct Debit.
+
+## Status
+[![npm version][npm-image]][npm-url] [![build status][travis-image]][travis-url]
+
+## Installation
+Install the package via `npm`:
+
+```sh
+npm install uk-modulus-checking --save
+```
+
+## Usage
+
+### `new UkModulusChecking({ accountNumber, sortCode }).isValid()`
+
+This method validates if the given accountNumber and sortCode represent a valid `Faster Payment Account`.
+
+#### Arguments
+
+1. `accountNumber` *(string)*: The account number to validate.
+2. `sortCode` *(string)*: The sort code to validate.
+
+#### Returns
+*(boolean)*:  Returns `true` if the account is valid.
+
+#### Example
+```js
+new UkModulusChecking({ accountNumber: '15764273', sortCode: '938063' }).isValid();
+// => false
+
+new UkModulusChecking({ accountNumber: '66374958', sortCode: '089999' }).isValid();
+// => true
+
+new UkModulusChecking({ accountNumber: '66374958', sortCode: '08-99-99' }).isValid();
+// => true
+
+new UkModulusChecking({ accountNumber: '66374958', sortCode: '08-9999' }).isValid();
+// => true
+```
+
+## Tests
+
+```sh
+npm test
+```
+
+## Release
+
+```sh
+npm version [<newversion> | major | minor | patch] -m "Release %s"
+```
+
+## License
+MIT
+
+## Credits
+Many thanks to [bazerk/uk-modulus-checking](https://github.com/bazerk/uk-modulus-checking) for the original inspiration.
+
+[npm-image]: https://img.shields.io/npm/v/uk-modulus-checking.svg?style=flat-square
+[npm-url]: https://npmjs.org/package/uk-modulus-checking
+[travis-image]: https://img.shields.io/travis/uphold/uk-modulus-checking.svg?style=flat-square
+[travis-url]: https://img.shields.io/travis/uphold/uk-modulus-checking.svg?style=flat-square

package.json

@@ -1,7 +1,7 @@
 {
   "name": "uk-modulus-checking",
   "version": "0.0.1",
-  "description": "Validating account numbers",
+  "description": "Validate a UK bank account number against a sort code using the VocaLink modulus check",
   "author": "Uphold",
   "license": "MIT",
   "homepage": "https://github.com/uphold/uk-modulus-checking",

src/constants.js

@@ -0,0 +1,19 @@
+
+/* jscs:disable validateOrderInObjectKeys */
+export const positions = {
+  u: 0,
+  v: 1,
+  w: 2,
+  x: 3,
+  y: 4,
+  z: 5,
+  a: 6,
+  b: 7,
+  c: 8,
+  d: 9,
+  e: 10,
+  f: 11,
+  g: 12,
+  h: 13
+};
+/* jscs:enable validateOrderInObjectKeys */