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https://github.com/bcherny/tsoption
Correct, easy to use Option type for TypeScript. 🦄
https://github.com/bcherny/tsoption
functional-programming monad scala typescript
Last synced: 5 days ago
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Correct, easy to use Option type for TypeScript. 🦄
- Host: GitHub
- URL: https://github.com/bcherny/tsoption
- Owner: bcherny
- Created: 2017-07-08T01:35:48.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2019-12-25T12:34:15.000Z (almost 5 years ago)
- Last Synced: 2024-10-18T11:27:01.727Z (19 days ago)
- Topics: functional-programming, monad, scala, typescript
- Language: TypeScript
- Homepage:
- Size: 91.8 KB
- Stars: 55
- Watchers: 3
- Forks: 2
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# tsoption [![Build Status][build]](https://circleci.com/gh/bcherny/tsoption) [![npm]](https://www.npmjs.com/package/tsoption) [![mit]](https://opensource.org/licenses/MIT) [![fantasy]](https://github.com/fantasyland/fantasy-land#monad)
[build]: https://img.shields.io/circleci/project/bcherny/tsoption.svg?branch=master&style=flat-square
[npm]: https://img.shields.io/npm/v/tsoption.svg?style=flat-square
[mit]: https://img.shields.io/npm/l/tsoption.svg?style=flat-square
[fantasy]: https://img.shields.io/badge/fantasyland-Monad-ff4ba4.svg?style=flat-square
> Correct, easy to use Option type for TypeScript. Like Scala options; see the [introductory blog post](https://performancejs.com/post/ewff3hj/Options-in-TypeScript).
## Installation
```sh
# Using Yarn:
yarn add tsoption
# Or, using NPM:
npm install tsoption --save
```
## Usage
*Note: You can use JavaScript instead of TypeScript, but it's not as fun.*
```ts
let a = Option.of(3) // Some(3)
.flatMap(_ => Some.of(5)) // Some(5)
.map(_ => 'a') // Some('a')
.orElse(Option.of('b')) // Some('a') (non-string type gives a compile error)
.getOrElse('c') // 'a'
let b = Option.of('a') // Some('a')
.flatMap(_ => new None) // None() (flatMap can map to any type)
.orElse(Option.of('b')) // Some('b') (non-string type gives a compile error)
.get() // 'b'
```
## API
*Note: The types of each of the expressions below are known at compile time.*
```ts
// Create an option
Option.of(3) // Some(3)
Option.of('abc') // Some('abc')
Option.of(null) // None (for convenience)
Option.of(undefined) // None (for convenience)
Some.of(3) // Some(3)
Some.of(null) // Some(null)
new Some([1, 2, 3]) // Some([1, 2, 3])
new None // None
// #flatMap
Some.of(3).flatMap(_ => Some.of(_ * 2)) // Some(6)
None.of().flatMap(() => Some.of(2)) // None
// #get
Some.of(3).get() // 3
None.of().get() // COMPILE ERROR! Can't call get() on None
// #getOrElse
Some.of(1).getOrElse(2) // 1
None.of().getOrElse(2) // 2
// #isEmpty
Some.of(2).isEmpty() // false (known at compile time too!)
None.of().isEmpty() // true (known at compile time too!)
// #map
Some.of(2).map(_ => _ * 2) // Some(4)
None.of().map(() => 2) // None (known at compile time too!)
// #nonEmpty
Some.of(2).nonEmpty() // true (known at compile time too!)
None.of().nonEmpty() // false (known at compile time too!)
// #orElse
Some.of(2).orElse(Option.of(3)) // Some(2)
None.of().orElse(Option.of(3)) // Some(3)
// #toString
Some.of(2).toString() // "Some(2)"
None.of().toString() // "None"
```
## Fantasyland
TSOption is [Fantasyland](https://github.com/fantasyland/fantasy-land)-compliant. It implements:
- [x] [Applicative](https://github.com/fantasyland/fantasy-land#applicative)
- [x] [Apply](https://github.com/fantasyland/fantasy-land#apply)
- [x] [Chain](https://github.com/fantasyland/fantasy-land#chain)
- [x] [Functor](https://github.com/fantasyland/fantasy-land#functor)
- [x] [Monad](https://github.com/fantasyland/fantasy-land#monad)
### Fantasyland-Compatible API
```ts
import * as fl from 'fantasy-land'
const {ap, chain, map, of} = fl
// Create an option
Option[of](3) // Some(3)
Option[of]('abc') // Some('abc')
Option[of](null) // None
Option[of](undefined) // None
// #chain
Option[of](3)[chain](_ => Option[of](_ * 2)) // Some(6)
Option[of](null)[chain](() => Option[of](2)) // None (known at compile time too!)
// #map
Option[of](2)[map](_ => _ * 2) // Some(4)
Option[of](null)[map](() => 2) // None (known at compile time too!)
// #ap
Option[of](2)[ap](Option[of]((_: number) => _ * 2)) // Some(4)
Option[of](null)[ap](Option[of](() => 2)) // None (known at compile time too!)
```
## Tests
```sh
npm test
```
## License
MIT