Result Monad for TypeScript

The Result pattern is a way of saying: "Hey, things might go wrong—and that's okay." Success and failure both deserve attention, and using Result means we're choosing to deal with uncertainty up front, not pretend it doesn't exist.

Installation

Deno

// Import from JSR
import { fail, ok, Result } from 'jsr:@szymdzum/result-monad';

// Or import specific version
import { fail, ok, Result } from 'jsr:@szymdzum/result-monad@0.1.2';

Node.js

# npm
npm install @szymdzum/result-monad

# yarn
yarn add @szymdzum/result-monad

# pnpm
pnpm add @szymdzum/result-monad

import { fail, ok, Result } from '@szymdzum/result-monad';

Basic Usage

import { fail, ok, Result } from '@szymdzum/result-monad';

// Create a success result
const success = ok(42);
console.log(success.isSuccess); // true
console.log(success.value); // 42

// Create a failure result
const failure = fail(new Error('Something went wrong'));
console.log(failure.isFailure); // true
console.log(failure.error.message); // "Something went wrong"

// Or use the Result class directly
const anotherSuccess = Result.ok('hello');
const anotherFailure = Result.fail(new Error('Another error'));

// Chain operations (only runs if previous operations were successful)
const result = await Result.fromPromise(fetchData())
  .map((data) => processData(data))
  .flatMap((processed) => validateData(processed));

// Handle result with pattern matching
const message = result.match(
  (value) => `Successfully processed: ${value}`,
  (error) => `Error: ${error.message}`,
);

Documentation

Full documentation is available in the docs folder:

• What is a Monad?
• Basic Usage
• Error Handling
• Async Patterns
• Validation
• Functional Composition

Development

# Run tests
deno task test

# Check types
deno task check

# Format code
deno task fmt

# Lint code
deno task lint

# Run tests with coverage
deno task coverage

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.