millsp/ts-toolbelt

★ 7,141TypeScriptAudience · developerComplexity · 2/5Setup · easy

Mindmap

mindmap
  root((repo))
    What it does
      Type transformations
      200-plus utilities
      No runtime code
    Categories
      Object types
      Function types
      String and union types
    Tech Stack
      TypeScript
      npm
    Use Cases
      Merge object types
      Transform union types
      Extract return types

mindmap root((repo)) What it does Type transformations 200-plus utilities No runtime code Categories Object types Function types String and union types Tech Stack TypeScript npm Use Cases Merge object types Transform union types Extract return types

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Things people build with this

USE CASE 1

Merge two TypeScript object types into one without writing complex custom type logic

USE CASE 2

Make specific fields of an existing type optional or required without redefining the whole type

USE CASE 3

Extract the exact return type of a function to reuse it elsewhere in your code

USE CASE 4

Filter or remap the members of a union type using built-in utilities

Tech stack

TypeScriptnpm

Getting it running

Difficulty · easy Time to first run · 5min

Requires TypeScript 4.1 or higher with strict mode enabled for best results.

In plain English

ts-toolbelt is a collection of over 200 utility types for TypeScript, a programming language that adds type annotations to JavaScript. In TypeScript, types describe the shape of data: what fields an object has, what a function accepts and returns, and so on. As programs grow, developers often need to transform or combine those types in sophisticated ways, and doing that from scratch can be complex. ts-toolbelt provides a ready-made library of those transformations. The library is organized around TypeScript's core concepts: object types, list types (arrays), function types, string types, union types, class types, boolean types, and number types. For each category there are many specific utilities. For example, you can merge two object types together, make certain fields optional, extract the return type of a function, split a string type into its parts, or filter the members of a union. These are things TypeScript supports in principle, but the logic to do them cleanly can take many lines of code to write yourself. The library describes itself as similar to utility libraries like lodash or ramda, but applied to the type level rather than to runtime data. Installing it does not add anything that runs in your application, it only adds type definitions that help the TypeScript compiler catch mistakes and understand your code better. Installation is through npm, the standard JavaScript package manager. The library requires TypeScript version 4.1 or higher and works best with strict type checking enabled. It has a full documentation site with entries for each utility, organized by category.

Copy-paste prompts

Prompt 1

Using ts-toolbelt, show me how to merge two TypeScript interfaces, one with user fields and one with account fields, into a single combined type.

Prompt 2

I have a TypeScript type with 10 fields and I want to make only 3 of them optional. How do I use ts-toolbelt to do that without rewriting the whole type?

Prompt 3

Using ts-toolbelt, how do I extract the return type of an async function and use it as the type for another variable?

Prompt 4

I have a union type of string literals and I want to filter out one member. Show me how to do that with ts-toolbelt.

Prompt 5

Walk me through setting up ts-toolbelt in a new TypeScript project with strict mode enabled, and show me a quick example of the Object.Merge utility.

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