https://github.com/yamafaktory/pattern-guard

JavaScript pattern guards 💂
https://github.com/yamafaktory/pattern-guard

guards haskell pattern-guard

Last synced: 5 days ago
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JavaScript pattern guards 💂

• Host: GitHub
• URL: https://github.com/yamafaktory/pattern-guard
• Owner: yamafaktory
• License: mit
• Created: 2017-02-01T23:26:54.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2020-05-05T14:18:55.000Z (over 4 years ago)
• Last Synced: 2024-10-01T15:44:09.857Z (about 1 month ago)
• Topics: guards, haskell, pattern-guard
• Language: JavaScript
• Size: 138 KB
• Stars: 68
• Watchers: 5
• Forks: 2
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Pattern-guard 💂 [![Build Status](https://travis-ci.org/yamafaktory/pattern-guard.svg?branch=master)](https://travis-ci.org/yamafaktory/pattern-guard) [![npm version](https://img.shields.io/npm/v/pattern-guard.svg?style=flat)](https://www.npmjs.com/package/pattern-guard) [![Standard - JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg)](http://standardjs.com/)

[![Greenkeeper badge](https://badges.greenkeeper.io/yamafaktory/pattern-guard.svg)](https://greenkeeper.io/)

Pattern-guard is a small module that brings you the [Haskell guards syntax](https://wiki.haskell.org/Pattern_guard) in JavaScript.

## Usage

```js

const guards = require('pattern-guard')

const [a, b, c] = [1, 3, 7]

const result = guards({ a, b, c })`

  | a > b = 1337

  | b > c = 999

  | c > a = 42

  | c > b = 11

`

console.log(result) // 42

```

Please note that, like in Haskell, the first truthy guard will be returned.

Guards can also be inlined:

```js

guards({ a, b, c })`a < b = 'yep' | b > c = 'nope' | c > a = 'maybe'`

```

And they support all comparison operators `< <= == === !== != >= >` and the logical operators too `&& || !`.

In Haskell, the `otherwise` keyword is used as a catch-all. To avoid using this keyword as variable name, this logic is not implemented in the module, you can simply emulate the same behaviour by using `true`:

``` js

const [a, b, c] = [1, 2, 3]

const result = guards({ a, b, c })`

  | a > b = 'nope'

  | b > c = 'nope'

  | c < a = 'nope'

  | true = 'yep'

`

console.log(result) // 'yep'

```

## Linting

The code quality is checked by the [JavaScript Standard Style](http://standardjs.com/).

## License

Released under the [MIT license](https://opensource.org/licenses/MIT) by Davy Duperron.