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ts-toolbelt is the largest, and most tested type library available right now, featuring +200 utilities. Our type collection packages some of the most advanced mapped types, conditional types, and recursive types on the market.

Spend less time, build stronger. Benefit from a wide range of generic type functions to achieve better type safety.

We work just like lodash, or ramda, but applied to the type system. Our mission is to provide you with simple ways to compute, change, and create types. We abstract all those complex type checks away for you. We provide a simple, reusable, and standard API to help you get more done with TypeScript.

ts-toolbelt is a well organized package that can help you perform advanced operations on object types, union types, as well as function, and literal types. It is carefully and coherently designed for building robust, flexible, and type-safe software.

We are a community and a knowledge base. Everyone is welcome to ask questions about types. If you are stuck or you misunderstand something, you came to the right place!. We welcome beginners and advanced developers to come take part. Welcome!

npm install typescript@^4.1.0 --save-dev

For best results, add this to your tsconfig.json

{
  "compilerOptions": {
    // highly recommended (required by few utilities)
    "strictNullChecks": true,

    // this is optional, but enable whenever possible
    "strict": true,

    // this is the lowest supported standard library
    "lib": ["es2015"],
  }
}

npm install ts-toolbelt --save

import {Object} from "ts-toolbelt"
// Check the docs below for more

// Merge two `object` together
type merge = Object.Merge<{name: string}, {age?: number}>
// {name: string, age?: number}

// Make a field of an `object` optional
type optional = Object.Optional<{id: number, name: string}, "name">
// {id: number, name?: string}

You can level-up, and re-code this library from scratch.

The project is organized around TypeScript's main concepts:

TIP How to choose categories? Match your type with them.

There are many ways to import the types into your project:

• Explicit

  import {Any, Boolean, Class, Function, Iteration, List, Number, Object, String, Union} from "ts-toolbelt"

• Compact

  import {A, B, C, F, I, L, N, O, S, U} from "ts-toolbelt"

• Portable

  import tb from "ts-toolbelt"

You can also import our non-official API from the community:

import {Community} from "ts-toolbelt"

TIP The community API is for our community to publish useful types that don't see fit in the standard API.

EXAMPLE https://millsp.github.io/ts-toolbelt/4.2.1/

In this wiki, you will find some extra resources for your learning, and understanding.

Are you missing something? Participate to the open-wiki by posting your questions.

To run the lint & type tests, simply run:

npm test

Want to test your own types? Let's get started:

import {Number, Test} from "ts-toolbelt"

const {checks, check} = Test

checks([
    check<Number.Add<1, 30>, 31, Test.Pass>(),
    check<Number.Add<5, -3>, 2,  Test.Pass>(),
])

TIP Place it in a file that won't be executed, it's just for TypeScript to test types.

The releases are done with Travis CI in stages & whenever a branch or PR is pushed:

• Tests are run with npm test
• Tests against DefinitelyTyped
• Releases to npm@[branch-name]

The project is maintained to adapt to the constant changes of TypeScript:

Major version numbers will upgrade whenever TypeScript had breaking changes.

Otherwise, the release versions will naturally follow the semantic versioning.

• Automated performance tests

  # performance is checked manually with 
  npx tsc --noEmit --extendedDiagnostics

• Need to write more examples