https://github.com/pedromsilvapt/data-either

Simple TypeScript/ES2017 class to represent either values
https://github.com/pedromsilvapt/data-either

Last synced: 11 days ago
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Simple TypeScript/ES2017 class to represent either values

• Host: GitHub
• URL: https://github.com/pedromsilvapt/data-either
• Owner: pedromsilvapt
• Created: 2018-01-31T11:59:27.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2018-04-25T12:32:59.000Z (over 6 years ago)
• Last Synced: 2024-10-06T15:18:12.005Z (3 months ago)
• Language: TypeScript
• Size: 4.88 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Either

> Simple TypeScript/ES2017 class to represent either values

# Installation

```shell

npm install --save data-either

```

# Usage

```typescript

import { Either } from 'data-either';

const left = Either.left( 1 );

const right = Either.right( 20 );

left.isRight(); // false

right.isRight(); // true

```

You can also convert trowable functions into either.

```typescript

import { Either } from 'data-either';

const left = Either.ofThrowable( () => 2 );

const right = Either.ofThrowable( () => { throw new Error(); } );

left.getLeft(); // 2

right.getRight(); // Error

```

Convert a Promise that can reject into an always resolved promise.

```typescript

import { Either } from 'data-either';

const left = Either.ofPromise( Promise.resolve( "left" ) );

const right = Either.ofPromise( Promise.reject( new Error() ) );

left.getLeft(); // "left"

right.getRight(); // Error

```

There are also a number of computations that can be done functionally with this module.

```typescript

import { Either } from 'data-either';

let value : Either = Either.left( 1 );

value = value.map( n => n * 3, err => `Error: ${ err }` ); // Either.left( 3 )

value = value.flatMap( n => n % 2 === 0 ? Either.left( n ) : Either.right( "Error: Not event." ), r => Either.right( r ) ); // Either.right( "Error: Not even." )

// Or simply

value = value.flatMapLeft( n => n % 2 === 0 ? Either.left( n ) : Either.right( "Error: Not event." ) ); // Either.right( "Error: Not even." )

value.leftOrElse( 0 ); // 0

```