monads

Result/Option types and Rust-style functional combinators for explicit, type-safe error handling.

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 and Effect 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

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 — install and use your first Result
• Result — Result<T, E> constructors, guards, and combinators
• ResultAsync — chaining async operations that can fail
• Option — Option<T> constructors, guards, and combinators
• Pipe — composing the standalone combinators

Runtime Support

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).