Installation

npm i @vyke/results

Examples

import * as fs from 'node:fs'
import { r } from '@vyke/results/r'

function readFile(filename: string) {
	try {
		return r.ok(fs.readFileSync(filename))
	}
	catch (error) {
		return r.err(new Error('error reading file'))
	}
}

const result = readFile('test.txt')
if (r.isOk(result)) {
	console.log(result.value) // the files content
}
else {
	console.error(result.value) // value is the error here
}

Using promises

import * as fs from 'node:fs/promises'
import { r } from '@vyke/results/r'

async function readFile(filename: string) {
	const result = await r.to(fs.readFile(filename))

	if (r.isErr(result)) {
		return r.err(new Error('error reading file'))
	}

	return result
}

const result = await readFile('test.txt')
if (r.isOk(result)) {
	console.log(result.value) // the files content
}
else if (r.isErr(result)) {
	console.error(result.value) // value is the error here
}

API

Ok

Creates a new successful result with the given value.

[!TIP] alias of r.ok

import { Ok } from '@vyke/results/result'

const result = Ok(123)
//      ^? Result<number, never>

Err

Creates a new error result with the given error.

[!TIP] alias of r.err

import { Err } from '@vyke/results/result'

const result = Err(new Error('some error'))
//      ^? Result<never, Error>

[!NOTE] Error values don't need to be an error, they can be anything.

isOk

Checks if the result is a successful result.

[!TIP] alias of r.isOk

isErr

Checks if the result is an error result.

[!TIP] alias of r.isErr

expectOk

Unwraps the value of a result or throws a custom error.

[!TIP] alias of r.expectOk

import { Err, Ok, expect } from '@vyke/results/result'

const value = expect(Ok(123), 'some error')
//     ^? number

expect(Err(new Error('some error')), 'another error') // throws the error with the message `another error`

unwrap

Unwraps the value of a result or throws an error.

[!TIP] alias of r.unwrap

import { Ok, unwrap } from '@vyke/results/result'

const value = unwrap(Ok(123))
//      ^? number
unwrap(Err(new Error('some error'))) // throws the error

unwrapOr

Unwraps the value of a result or returns a default value.

[!TIP] alias of r.unwrapOr

import { Ok, unwrapOr } from '@vyke/results/result'

const value = unwrapOr(Ok(123), 10)
//      ^? number
unwrapOr(Err(new Error('some error')), 10) // returns 10 instead of the error

mapInto

Maps the value of a result to a new result using the provided mapping function.

[!TIP] alias of r.mapInto

import { Err, Ok, mapInto } from '@vyke/results/result'
mapInto(Ok(1), (value) => Ok(value + 1)) // Ok(2)
mapInto(Err(new Error('some error')), (value) => Ok(value + 1)) // Err(new Error('some error'))

MapHelper

A helper class for chaining map operations on a result.

map

A helper class for chaining map operations on a result.

[!TIP] alias of r.map

import { Err, Ok, map } from '@vyke/results/result'

map(Ok(1))
	.into((value) => Ok(value + 1))
	.into((value) => Ok(value + 1))
	.done()

capture

Runs a function and captures any errors, converting them to a result.

[!TIP] alias of r.capture

import { Err, Ok, capture, unwrap } from '@vyke/results/result'

const result1 = capture(() => 123) // only returns value in a return
//     ^? Result<number, unknown>

const result2 = capture(() => {
	unwrap(Err(new Error('some error')))
})

flatten

Flattens a nested result.

[!TIP] alias of r.flatten

import { Ok, flatten } from '@vyke/results/result'

const result = flatten(Ok(Ok(123)))
//      ^? Result<number, unknown>

to

Converts a promise to a result

[!TIP] alias of r.to

import { to } from '@vyke/results/result'

const result = await to(Promise.resolve(123))
//     ^? Result<number, unknown>

[!CAUTION] Notice that Result error type is unknown

andThen

Converts a promise to a result and applies a mapping function

[!TIP] alias of r.andThen

import { Ok, andThen } from '@vyke/results/result'

const result = andThen(Ok(123), (value) => Ok(String(value)))
//      ^? Result<number, never>

next

Creates a function to be used as a then callback in a promise chain

[!TIP] alias of r.next

import { next, to } from '@vyke/results/result'

const result = await Promise.resolve(Ok(123))
//     ^? Result<string, never>
	.then(next((value) => Ok(String(value))))

toExpectOk

Converts a promise to a result and throws an error with a custom message if the result is an error

[!TIP] alias of r.toExpect

import { Err, Ok, toExpectOk } from '@vyke/results/result'

const value = await toExpectOk(Ok(123), 'some error')
//     ^? number
await toExpectOk(Err(new Error('some error')), 'another error') // throws the error with the message `another error`

toUnwrap

Awaits for the promise and unwraps it then returns the value or throws the error

[!TIP] alias of r.toUnwrap

import { Ok, toUnwrap } from '@vyke/results/result'

const value = await toUnwrap(Ok(123))
//      ^? number
await toUnwrap(Err(new Error('some error'))) // throws the error

toUnwrapOr

Awaits for the promise, unwraps it, and then returns the value or the default one

[!TIP] alias of r.toUnwrapOr

import { Ok, toUnwrapOr } from '@vyke/results/result'

const value = await toUnwrapOr(Ok(123), 345)
//      ^? number
await toUnwrapOr(Err(new Error('some error')), 456) // returns 456 instead of throwing

r

Shorthand for all functions in the result module for easy access

Some

Creates a new Some option.

[!TIP] alias of o.Some

None

Creates a new None option.

isSome

Checks if an option is a Some option.

[!TIP] alias of o.isSome

import { None, Some, isSome } from '@vyke/results/option'

isSome(Some(123)) // true
isSome(None()) // false
const option = Some(123)
if (isSome(option)) {
	console.log(option.value) // safe to access value
}

isNone

Checks if an option is a None option.

[!TIP] alias of o.isNone

import { None, Some, isNone } from '@vyke/results/option'

isNone(Some(123)) // false
isNone(None()) // true

unwrap

Unwraps the value of an option or throws an error.

[!TIP] alias of o.unwrap

import { None, Some, unwrap } from '@vyke/results/option'

const value = unwrap(Some(123))
//      ^? number 123
unwrap(None()) // throws an Error Result

unwrapOr

Unwraps the value of a result or returns a default value.

[!TIP] alias of o.unwrapOr

import { None, Some, unwrapOr } from '@vyke/results/option'

const value = unwrapOr(Some(123), 10)
//      ^? number
unwrapOr(None(), 10) // returns 10 instead of throwing an error

o

Shorthand for all functions in the result module for easy access

Others vyke projects

• Flowmodoro app by vyke
• @vyke/tsdocs
• @vyke/val
• @vyke/dom