ts-pattern

What is ts-pattern?

ts-pattern is a pattern matching library for TypeScript that allows for expressive and type-safe pattern matching. It provides a way to handle complex data structures and control flow in a concise and readable manner.

What are ts-pattern's main functionalities?

Basic Pattern Matching

This feature allows you to match a value against multiple patterns and execute corresponding actions. The 'otherwise' method provides a default case.

const { match } = require('ts-pattern');

const value = 2;
const result = match(value)
  .with(1, () => 'one')
  .with(2, () => 'two')
  .with(3, () => 'three')
  .otherwise(() => 'unknown');

console.log(result); // Output: 'two'

Nested Pattern Matching

This feature allows you to match nested objects and structures, making it easier to handle complex data.

const { match } = require('ts-pattern');

const data = { type: 'user', user: { name: 'Alice', age: 30 } };
const result = match(data)
  .with({ type: 'user', user: { name: 'Alice' } }, () => 'Hello Alice')
  .with({ type: 'user', user: { age: 30 } }, () => 'User is 30 years old')
  .otherwise(() => 'Unknown user');

console.log(result); // Output: 'Hello Alice'

Guard Functions

Guard functions allow you to use custom logic to determine if a pattern matches, providing greater flexibility.

const { match, when } = require('ts-pattern');

const value = 10;
const result = match(value)
  .with(when(x => x > 5), () => 'greater than 5')
  .with(when(x => x <= 5), () => '5 or less')
  .otherwise(() => 'unknown');

console.log(result); // Output: 'greater than 5'

Other packages similar to ts-pattern

match-ts

match-ts is another TypeScript pattern matching library. It offers similar functionality to ts-pattern but with a different API design. It focuses on providing a more functional programming style.

typescript-pattern-matching

typescript-pattern-matching is a library that provides pattern matching capabilities for TypeScript. It is similar to ts-pattern but may have different performance characteristics and API design choices.

fp-ts

fp-ts is a library for functional programming in TypeScript. While it is not solely focused on pattern matching, it provides utilities for handling data structures and control flow in a functional style, which can be used to achieve similar outcomes.

README

Typescript Pattern

A complete pattern matching library for typescript.