Crab Salad

A lightweight TypeScript library for Result<T, E> and Option<T>, inspired by Rust.

Disclaimer

This project provides a beautiful and expressive way to handle errors and optional values using functional-style constructs like Result and Option. It aims to improve code readability and robustness in a way inspired by languages like Rust.

However, this approach does not follow the idiomatic or native error-handling patterns of JavaScript/TypeScript, such as exceptions and nullable types.

Therefore, while it's a useful learning tool or for internal experimentation, I do not recommend using this in production environments.

Use it to explore better patterns — but weigh it against the expectations and conventions of the JS/TS ecosystem.

Installation

npm install crab-salad

Result<T, E>

Represents either a successful value (Ok) or an error (Err).

import { Ok } from 'crab-salad';

const result = Ok(5).map((x) => x * 2); // Ok(10)

if (result.isOk) {
  console.log(result.unwrap());
}

API

• Ok(value)
• Err(error)

• result.and(other)
• result.andThen(fn)
• result.err()
• result.expect(msg)
• result.expectErr(msg)
• result.flatten()
• result.inspectOk(fn)
• result.inspectErr(fn)
• result.isErr
• result.isErrAnd(fn)
• result.isOk
• result.isOkAnd(fn)
• result.map(fn)
• result.mapErr(fn)
• result.mapOr(other, fn)
• result.mapOrElse(otherFn, fn)
• result.ok()
• result.or(other)
• result.orElse(fn)
• result.transpose()
• result.unwrap()
• result.unwrapErr()
• result.unwrapOr(other)
• result.unwrapOrElse(fn)

• Result.fromPromise(promise, mapErr)
• Result.fromAsyncFn(fn, mapErr)
• result.match({ ok, err })
• result.toPromise()
• Result.tryCatch(fn, mapErr)
• result.unzip()
• result.zip(other)
• result.zipWith(other, fn)

Option<T>

Represents an optional value: Some(value) or None.

import { Option } from 'crab-salad';

const maybeName = Option.fromNullable('Alice');

maybeName.match({
  some: (val) => console.log('Name:', val),
  none: () => console.log('No name found'),
});

API

• Some(value)
• None()

• option.and(other)
• option.andThen(fn)
• option.expect(msg)
• option.filter(fn)
• option.flatten()
• option.inspectSome(fn)
• option.isNone
• option.isNoneOr(fn)
• option.isSome
• option.isSomeAnd(fn)
• option.map(fn)
• option.mapOr(other, fn)
• option.mapOrElse(fn, fn)
• option.okOr(err)
• option.okOrElse(fn)
• option.or(other)
• option.orElse(fn)
• option.transpose()
• option.unwrap()
• option.unwrapOr(other)
• option.unwrapOrElse(fn)
• option.unzip()
• option.xor(other)
• option.zip(other)
• option.zipWith(other, fn)

• Option.fromNullable(val)
• option.match({ some, none })
• option.toNullable()
• option.toUndefined()

Docs

See Docs for full working examples of each method.

Running Tests

npm run test

Uses Vitest for fast TypeScript unit testing.

Changelog

See CHANGELOG.md for a list of changes.

License

MIT