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Overview

It is a TypeScript implementation of Rust's Option and Result types.

It is a playground library that closely mirrors Rust's Option and Result API. While created primarily for fun and learning, it's robust enough for real-world applications. It allows for safer, more expressive handling of optional values through a monadic interface. Snake_case is used for the plausibility of the original.

The name unwrap-or is a playful reference to both the unwrap_or method found in the Option/Result types, and a hint at the package's contents - "-OR" standing for Option and Result types. It also cleverly references the logical OR operation, reflecting how these monadic types encapsulate one of two possible states - either Some or None for Option; either Ok or Err for Result.

Installation​

Via npm:

npm install unwrap-or

You can also use your favorite package manager:

# pnpm
pnpm add unwrap-or

# bun
bun add unwrap-or

# yarn
yarn add unwrap-or

# deno
deno add npm:unwrap-or

Modules​

JavaScript/TypeScript use null or undefined types to represent empty outputs, and exceptions to handle errors. Instead, there are two special generic variants - Option and Result could be used to deal with above cases.

Option​

Optional values.

Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not.

Basic usages​

import { type Option, Some, None } from "unwrap-or/option";

When writing a function or data type:

  • if an argument of the function is optional
  • if the function is non-void and if the output it returns can be empty
  • if the value of a property of the data type can be empty
interface Bio {
  name: string;
  middle_name: Option<string>;
  last_name: string;
}
function divide(numerator: number, denominator: number): Option<number> {
  return denominator === 0 ? Some(numerator / denominator) : None;
}

See the module level documentation for more.

Result​

Error handling with the Result type.

Type Result is used for returning and propagating errors: every Result is either Ok - representing success and containing a value, or Err - representing error and containing an error value.

Basic usages​

import { type Result, Ok, Err } from "unwrap-or/result";

If a function can produce an error, by combining the data type of the valid output and the data type of the error.

functuion invariant(predicate: boolean, message: string): Result<boolean, message> {
  return predicate ? Ok(predicate) : Err(message);
}

See the module level documentation for more.

Inspirations​

  • fnts - minimal functional programming utilities for TypeScript & JavaScript inspired by the programming language Haskell.

  • ts-expression - pair constructor, binary representation, a minimal implementation of Lisp's symbolic expressions (s-expressions) for TypeScript.

License​

Made by a human being, not LLM.

Copyright © 2025 Roman Hnatiuk

Licensed under MIT.