---
title: monads
description: Result/Option types and Rust-style functional combinators for explicit, type-safe error handling.
sidebar:
  label: Overview
type: package
package: "@zap-studio/monads"
---

`monads` provides `Result`, `ResultAsync`, and `Option` types with Rust-style functional combinators — an explicit, type-safe alternative to throw/catch and nullable checks.

## Motivation

Hand-rolled `{ ok: boolean, ... }` result shapes and nullable checks are easy to write once and painful to keep consistent across a codebase. Libraries like [neverthrow](https://github.com/supermacro/neverthrow) and [Effect](https://effect.website/) solve this well, but pull in more surface (do-notation, a runtime, generators, `Either`, class-based fluent APIs) than most projects need.

`monads` is deliberately small: `Result`, `ResultAsync`, and `Option`, as standalone, tree-shakeable functions composed with `pipe` — not class instances with chained methods.

## Features

- **`Result<T, E>`** — `ok`/`err` constructors, `isOk`/`isErr` guards, and `Result.map`/`Result.mapErr`/`Result.andThen`/`Result.unwrapOr`/`Result.unwrapOrElse`/`Result.unwrap`/`Result.match` combinators.
- **`ResultAsync<T, E>`** — a thenable wrapper around `Promise<Result<T, E>>`, awaitable directly, with chainable combinators for building async pipelines before the final `await`.
- **`Option<T>`** — `some`/`none` constructors, `isSome`/`isNone` guards, and the mirrored `Option` combinators.
- **Bridges** — `fromThrowable`, `fromPromise`, `fromNullable`.
- **`pipe`** — left-to-right composition for the standalone combinators above.
- **Zero dependencies, tree-shakeable.**

## Quick Start

```ts
import { err, ok, pipe, Result } from "@zap-studio/monads";

function parseAge(input: string): Result<number, string> {
  const value = Number(input);
  return Number.isNaN(value) ? err("not a number") : ok(value);
}

const message = pipe(
  parseAge("42"),
  Result.map((age) => age + 1),
  Result.match({
    ok: (age) => `Age next year: ${age}`,
    err: (reason) => `Invalid input: ${reason}`,
  }),
);
```

## Learn More

- [Getting Started](/monads/getting-started) — install and use your first `Result`
- [Result](/monads/result) — `Result<T, E>` constructors, guards, and combinators
- [ResultAsync](/monads/result-async) — chaining async operations that can fail
- [Option](/monads/option) — `Option<T>` constructors, guards, and combinators
- [Pipe](/monads/pipe) — composing the standalone combinators

## Runtime Support

| Runtime            | Minimum version                                  |
| ------------------ | ------------------------------------------------ |
| Node.js            | 18.0.0                                           |
| Bun                | 1.0.0                                            |
| Deno               | 1.42                                             |
| Cloudflare Workers | Any current release                              |
| Browsers           | Latest evergreen (Chrome, Edge, Firefox, Safari) |

The package ships standard ESM only and uses no runtime-specific APIs. Deno 1.42 is the first release that can install packages from JSR (`deno add jsr:@zap-studio/monads`).