Higher-Order TypeScript (HOTScript)

A library of composable functions for the type level!

Transform your TypeScript types in any way you want using functions you already know.

Features

• Type-level higher-order functions (Tuples.Map, Tuples.Filter, Objects.MapValues, etc).
• Type-level pattern matching with Match.
• Performant math operations (Numbers.Add, Numbers.Sub, Numbers.Mul, Numbers.Div, etc).
• Custom "lambda" functions.

🚧 work in progress 🚧

Installation

You can find HotScript on npm:

npm install -D hotscript

HotScript is a work-in-progress library, so expect breaking changes in its API.

Examples

Transforming a list

Run this as a TypeScript Playground

import { Pipe, Tuples, Strings, Numbers } from "hotscript";

type res1 = Pipe<
  //  ^? 62
  [1, 2, 3, 4],
  [
    Tuples.Map>,       // [4, 5, 6, 7]
    Tuples.Join<".">,                 // "4.5.6.7"
    Strings.Split<".">,               // ["4", "5", "6", "7"]
    Tuples.Map>, // ["14", "15", "16", "17"]
    Tuples.Map,     // [14, 15, 16, 17]
    Tuples.Sum                        // 62
  ]
>;

Defining a first-class function

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import { Call, Fn, Tuples } from "hotscript";

// This is a type-level "lambda"!
interface Duplicate extends Fn {
  return: [this["arg0"], this["arg0"]];
}

type result1 = Call, [1, 2, 3, 4]>;
//     ^? [[1, 1], [2, 2], [3, 3], [4, 4]]

type result2 = Call, [1, 2, 3, 4]>;
//     ^? [1, 1, 2, 2, 3, 3, 4, 4]

Transforming an object type

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import { Pipe, Objects, Booleans } from "hotscript";

// Let's compose some functions to transform an object type:
type ToAPIPayload = Pipe<
  T,
  [
    Objects.OmitBy>,
    Objects.Assign<{ metadata: { newUser: true } }>,
    Objects.SnakeCaseDeep,
    Objects.Assign<{ id: string }>
  ]
>;
type T = ToAPIPayload<{
  id: symbol;
  firstName: string;
  lastName: string;
}>;
// Returns:
type T = {
  id: string;
  metadata: { new_user: true };
  first_name: string;
  last_name: string;
};

Parsing a route path

Run this as a TypeScript Playground

https://user-images.githubusercontent.com/2315749/222081717-96217cd2-ac89-4e06-a942-17fbda717cd2.mp4

import { Pipe, Objects, Strings, ComposeLeft, Tuples, Match } from "hotscript";

type res5 = Pipe<
  //    ^? { id: string, index: number }
  "/users//posts/",
  [
    Strings.Split<"/">,
    Tuples.Filter>,
    Tuples.Map">, Strings.Split<":">]>>,
    Tuples.ToUnion,
    Objects.FromEntries,
    Objects.MapValues<
      Match<[Match.With<"string", string>, Match.With<"number", number>]>
    >
  ]
>;

API

• [x] Core
  • [x] Pipe
  • [x] PipeRight
  • [x] Call
  • [x] Apply
  • [x] PartialApply
  • [x] Compose
  • [x] ComposeLeft
• [x] Function
  • [x] ReturnType
  • [x] Parameters
  • [x] Parameter
  • [x] MapReturnType
  • [x] MapParameters
• [ ] Tuples
  • [x] Create -> [X]
  • [x] Partition
  • [x] IsEmpty
  • [x] Zip<...Tuple[]>
  • [x] ZipWith
  • [x] Sort
  • [x] Head
  • [x] Tail
  • [x] At
  • [x] Last
  • [x] FlatMap
  • [x] Find
  • [x] Drop
  • [x] Take
  • [x] TakeWhile
  • [x] GroupBy
  • [x] Join
  • [x] Map
  • [x] Filter
  • [x] Reduce
  • [x] ReduceRight
  • [x] Reverse
  • [x] Every
  • [x] Some
  • [x] SplitAt
  • [x] ToUnion
  • [x] ToIntersection
  • [x] Prepend
  • [x] Append
  • [x] Concat
  • [x] Min
  • [x] Max
  • [x] Sum
• [ ] Object
  • [x] Readonly
  • [x] Mutable
  • [x] Required
  • [x] Partial
  • [x] ReadonlyDeep
  • [x] MutableDeep
  • [x] RequiredDeep
  • [x] PartialDeep
  • [x] Update
  • [x] Record
  • [x] Keys
  • [x] Values
  • [x] AllPaths
  • [x] Create
  • [x] Get
  • [x] FromEntries<[Key, Value]>
  • [x] Entries
  • [x] MapValues
  • [x] MapKeys
  • [x] Assign<...Obj>
  • [x] Pick
  • [x] PickBy
  • [x] Omit
  • [x] OmitBy
  • [x] CamelCase
  • [x] CamelCaseDeep
  • [x] SnakeCase
  • [x] SnakeCaseDeep
  • [x] KebabCase
  • [x] KebabCaseDeep
• [ ] Union
  • [x] Map
  • [x] Extract
  • [x] ExtractBy
  • [x] Exclude
  • [x] ExcludeBy
  • [x] NonNullable<u>
  • [x] ToTuple<u>
  • [x] ToIntersection<u>
• [ ] String
  • [x] Length
  • [x] TrimLeft
  • [x] TrimRight
  • [x] Trim
  • [x] Join
  • [x] Replace
  • [x] Slice
  • [x] Split
  • [x] Repeat
  • [x] StartsWith
  • [x] EndsWith
  • [x] ToTuple
  • [x] ToNumber
  • [x] ToString
  • [x] Prepend
  • [x] Append
  • [x] Uppercase
  • [x] Lowercase
  • [x] Capitalize
  • [x] Uncapitalize
  • [x] SnakeCase
  • [x] CamelCase
  • [x] KebabCase
  • [x] Compare
  • [x] Equal
  • [x] NotEqual
  • [x] LessThan
  • [x] LessThanOrEqual
  • [x] GreaterThan
  • [x] GreaterThanOrEqual
• [ ] Number
  • [x] Add
  • [x] Multiply
  • [x] Subtract
  • [x] Negate
  • [x] Power
  • [x] Div
  • [x] Mod
  • [x] Abs
  • [x] Compare
  • [x] GreaterThan
  • [x] GreaterThanOrEqual
  • [x] LessThan
  • [x] LessThanOrEqual
• [ ] Boolean
  • [x] And
  • [x] Or
  • [x] XOr
  • [x] Not
  • [x] Extends
  • [x] Equals
  • [x] DoesNotExtend