@deessejs/core

Functional programming patterns for TypeScript.

Packages

Package	Description	Version
@deessejs/core	Functional programming patterns

Requirements

• TypeScript 5.0+
• Node.js 20+

Installation

# Install core
npm install @deessejs/core

# Or using pnpm
pnpm add @deessejs/core

# Or using yarn
yarn add @deessejs/core

Documentation

For full documentation, visit core.deessejs.com.

Quick Start

import { ok, err, isOk, isErr, Result } from '@deessejs/core'

// Ok - Normal Operation Result
const ok = ok({ id: 1, name: 'John' })

if (isOk(ok)) {
  console.log(ok.value.name)
}

// Err - Domain Errors
const notFound = err({
  name: 'NOT_FOUND',
  message: 'User not found',
  data: { id: 123 }
})

Maybe Type

The Maybe type represents optional values - a value that may or may not be present. It's a safer alternative to null/undefined.

Types

Type	Description
Maybe<T>	Union of Some<T> or None
Some<T>	A present value ({ ok: true, value: T })
None	An absent value ({ ok: false })

Functions

import {
  some, none,
  fromNullable, isSome, isNone,
  map, flatMap, getOrElse, getOrCompute,
  tap, match, toNullable, toUndefined
} from '@deessejs/core'

// Creation
const present = some(42)           // Some<number>
const absent = none()              // None

// From nullable
const value1 = fromNullable(42)    // Some<number>
const value2 = fromNullable(null)  // None
const value3 = fromNullable(0)     // Some<number> (0 is a valid value)

// Type guards
isSome(present)   // true
isNone(absent)    // true

// Transform
map(present, x => x * 2)           // Some<84>
flatMap(present, x => some(x * 2)) // Some<84>
flatMap(absent, x => some(x * 2))  // None

// Extract
getOrElse(present, 0)              // 42
getOrElse(absent, 0)               // 0

// Side effects
tap(present, console.log)           // logs 42, returns Some<42>
match(present, v => v * 2, () => 0) // 84
match(absent, v => v * 2, () => 0)  // 0

// Convert back
toNullable(present)  // 42
toNullable(absent)  // null
toUndefined(present) // 42
toUndefined(absent)  // undefined

Development

# Install dependencies
pnpm install

# Build all packages
pnpm build

# Run tests
pnpm test

# Run tests with coverage
pnpm test:coverage

# Lint
pnpm lint

# Type check
pnpm typecheck

Contributing

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

Author

• Nesalia Inc.

Security

If you discover any security vulnerabilities, please send an e-mail to security@nesalia.com.

License

MIT License - see the LICENSE file for details.