Types-Belt 🎯

A comprehensive collection of TypeScript utility types for building robust and maintainable applications. Types-Belt provides a wide range of utility types that help you write better TypeScript code with improved type safety and developer experience.

✨ Features

• Object Utilities: Transform object properties (Partial, Required, Readonly, Pick, Omit, etc.)
• Function Utilities: Extract function types, parameters, and return types
• Array & Tuple Utilities: Advanced array and tuple manipulation types
• Conditional Types: Type guards and conditional type utilities
• Production Ready: Well-tested and documented for production use
• Zero Dependencies: Pure TypeScript with no runtime dependencies

🚀 Installation

npm install types-belt

yarn add types-belt

pnpm add types-belt

📖 Usage

Object Utility Types

import type { Partial, Required, Readonly, Pick, Omit, Record } from 'types-belt';

interface User {
  id: number;
  name: string;
  email: string;
  password: string;
}

// Make all properties optional
type PartialUser = Partial<User>;
// Result: { id?: number; name?: string; email?: string; password?: string; }

// Make all properties required
type RequiredUser = Required<User>;
// Result: { id: number; name: string; email: string; password: string; }

// Make all properties readonly
type ReadonlyUser = Readonly<User>;
// Result: { readonly id: number; readonly name: string; readonly email: string; readonly password: string; }

// Pick specific properties
type UserPublic = Pick<User, 'id' | 'name' | 'email'>;
// Result: { id: number; name: string; email: string; }

// Omit specific properties
type UserWithoutPassword = Omit<User, 'password'>;
// Result: { id: number; name: string; email: string; }

// Create a record type
type UserRoles = Record<'admin' | 'user' | 'guest', boolean>;
// Result: { admin: boolean; user: boolean; guest: boolean; }

Function Utility Types

import type { ReturnType, Parameters, FirstParameter, LastParameter } from 'types-belt';

type MyFunction = (name: string, age: number) => Promise<boolean>;

// Extract return type
type ReturnType = ReturnType<MyFunction>; // Promise<boolean>

// Extract parameter types
type Params = Parameters<MyFunction>; // [string, number]

// Extract first parameter
type FirstParam = FirstParameter<MyFunction>; // string

// Extract last parameter
type LastParam = LastParameter<MyFunction>; // number

Array & Tuple Utility Types

import type { ArrayElement, Tuple, FirstElement, LastElement } from 'types-belt';

// Extract element type from array
type StringArray = string[];
type ElementType = ArrayElement<StringArray>; // string

// Create tuple with specific length
type StringTuple3 = Tuple<string, 3>; // [string, string, string]

// Extract first and last elements
type MyTuple = [string, number, boolean];
type First = FirstElement<MyTuple>; // string
type Last = LastElement<MyTuple>; // boolean

Conditional Utility Types

import type { Is, Extends, If, IsUnion, IsArray, IsFunction } from 'types-belt';

// Check if types are exactly equal
type IsString = Is<string, string>; // true
type IsNumber = Is<string, number>; // false

// Check if type extends another
type CanAssign = Extends<string, string | number>; // true

// Conditional type selection
type Result = If<true, string, number>; // string

// Type guards
type IsUnionType = IsUnion<string | number>; // true
type IsArrayType = IsArray<string[]>; // true
type IsFunctionType = IsFunction<() => void>; // true

🧪 Testing

Run the test suite to ensure all types work correctly:

# Run tests in watch mode
npm test

# Run tests once
npm run test:run

# Run tests with coverage
npm run test:coverage

# Type checking
npm run type-check

🏗️ Building

Build the package for distribution:

npm run build

This will create the following outputs in the dist/ directory:

• types-belt.es.js - ES Module format
• types-belt.cjs - CommonJS format
• index.d.ts - TypeScript declarations
• Source maps

📦 Publishing

Before publishing to npm, the package will automatically:

1. Build the project
2. Run all tests
3. Ensure everything passes

npm publish

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Inspired by the TypeScript community's need for better utility types
• Built with modern TypeScript features and best practices
• Tested with Vitest for reliable type validation

Made with ❤️ for the TypeScript community