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#software-engineering
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#software-engineering/typescript
> [!info] see more
> [hotscript/README.md at main · gvergnaud/hotscript (github.com)](https://github.com/gvergnaud/hotscript/blob/main/README.md)
> you might also want to check out [ts-essentials/ts-essentials: All basic TypeScript types in one place 🤙 (github.com)](https://github.com/ts-essentials/ts-essentials)
# 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:
```ts
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](https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgBWGApgGjgFQK5gA26AztgMoxTAB2A5mXAHJ4gBG6UJcAvnAGZQIIOACIAFhBgkAxtTAxRAbgBQKmAE8McKKQCMcALwo06ADwq4cAPTWrAPQD8cAGwAmS3ADae7G+wAzNgALAC6mJ5enlb4RKQAdACyAIZgZizsnCTxAIIAJnlmAQB8xdhWFTZ2XsHYAKzYLtgA7KHRuATE2QBSELRmovGiZZWjY1a2YsHxdfEu8c2i7ZTU9NnkRMAwA0Mj4+OTXqLBotiidadiLpeii22VsV1JqWYrtAzxyLoYNIWiesMRod-icznoLmDrmC7u1HgkUmk3mt4jgIBkOFA9hVDnpanBwdg9E18a1YZ0EuRWPtqQc7O5PG1ikogA)
<!-- prettier-ignore -->
```ts
import { Pipe, Tuples, Strings, Numbers } from "hotscript";
type res1 = Pipe<
// ^? 62
[1, 2, 3, 4],
[
Tuples.Map<Numbers.Add<3>>, // [4, 5, 6, 7]
Tuples.Join<".">, // "4.5.6.7"
Strings.Split<".">, // ["4", "5", "6", "7"]
Tuples.Map<Strings.Prepend<"1">>, // ["14", "15", "16", "17"]
Tuples.Map<Strings.ToNumber>, // [14, 15, 16, 17]
Tuples.Sum // 62
]
>;
```
#### Defining a first-class function
[Run this as a TypeScript Playground](https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgYQIYBt0Bo4DEB2OAKgK5joCmAznAL5wBmUEIcARABYQxUDGUwMDDYBuAFBiA9JLhEOwGgrio4MAJ5gKAWkoA3CunbpUIAEYATVGwCEY4PhgUoDVLwpwAImXTBeqR3AUAB6O+OY0BIhicHBQFDAkUPgAXHAA2jDyVGlsqFAA5gAMbAC6OJkKOXlFpSXitBLqmrHUJOgwAIxwALwoGOgAPKTk1AB0ALKoYANe5L7+FAB8OGkdOABMOADMOAAsJYvi0jEnAHoA-I0a7nFUbTDrPX2YQ95juMYwk9OzPn6Oy3SazgmzgOzg+0OUhkJzgFyAA)
```ts
import { Call, Fn, Tuples } from "hotscript";
// This is a type-level "lambda"!
interface Duplicate extends Fn {
return: [this["arg0"], this["arg0"]];
}
type result1 = Call<Tuples.Map<Duplicate>, [1, 2, 3, 4]>;
// ^? [[1, 1], [2, 2], [3, 3], [4, 4]]
type result2 = Call<Tuples.FlatMap<Duplicate>, [1, 2, 3, 4]>;
// ^? [1, 1, 2, 2, 3, 3, 4, 4]
```
#### Transforming an object type
[Run this as a TypeScript Playground](https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgBWGApgGjgeQEYBW6AxjAM7YBCEEANugIYB2ZcAvnAGZQQhwBEACwjliUNDH4BuAFAyA9PLgAZdDADkrYr0hl0cMr32cArk1LAILODAg2ozMp2h9mcCIRLwYATwwAuGV8MOAAVCABBZABJZAYfWggGABMAHlCAPjgAXhQ0dFSZODDMIrgAbTLi-CJSMgA6HBBgGEofVOo6RhZ6gFEARxMGWjJUsh8QPDoMjNLi6s86+oiyMmAAcyZUpBA1FIYYBn9EOCZ0AHcAVT0oY5goE30ONlmq3EXyeoBlJgYAa3QAGEGHoACLodBgObzGpeBorNabbZwYDJY5ke7AJjrdgZMoAXRkGVkwX0UWi13QUByYUiMTiCSSaQQZUU8wAegB+Mqo9ETKa0WTFTjAKAYgByDF26Mx2KFcFoIJgkulBll61kL1kbIASmoTFAWIFSWEaSziry1eI5WVdodkgcjiczucAPomG53B5PeUisUwV2-VUY60asqKjGBqXoGWhzVSIA)
```ts
import { Pipe, Objects, Booleans } from "hotscript";
// Let's compose some functions to transform an object type:
type ToAPIPayload<T> = Pipe<
T,
[
Objects.OmitBy<Booleans.Equals<symbol>>,
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://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgBWGApgGjgeQEYBW6AxjAM7YDKMUwAdgOYVwDCE4EZ6AMugGYxsAFQCuYADbpmAWQCGMYgAs4AXzh8o7OACJFEcsVpgY2gNwAoczACeGOFCkBWOAF4UadAB5zcOAHo-X18APQB+Hx0-ES4oMj9PYAATAC4yGnoGAD4-SDS4hLpE9AAPZLoREDx0KEztTAiAbQjfalpGMgA6SglgGE9tP21M+qC4UQkpDoAxYHEYas9WjM7qWVgyAHVexX7+zOHmsbFJTrkwb1HfNg4uXgFPJsugpfaOoVoQXe04AB8dWoOTxa6Ve3XEvX6ySGI0uAF1ModAUFxic3hAAKp0YAQOgw3z4IikTpTTQgACidHSUjxuEIJHIHTOADVZOIRFILpc5Aodo8gdylB0tjAdto0m0GHU4OKMkingLFELtv1ypVqlLVVUaodfPDERFYeZMqYgA)
https://user-images.githubusercontent.com/2315749/222081717-96217cd2-ac89-4e06-a942-17fbda717cd2.mp4
```ts
import { Pipe, Objects, Strings, ComposeLeft, Tuples, Match } from "hotscript";
type res5 = Pipe<
// ^? { id: string, index: number }
"/users/<id:string>/posts/<index:number>",
[
Strings.Split<"/">,
Tuples.Filter<Strings.StartsWith<"<">>,
Tuples.Map<ComposeLeft<[Strings.Trim<"<" | ">">, Strings.Split<":">]>>,
Tuples.ToUnion,
Objects.FromEntries,
Objects.MapValues<
Match<[Match.With<"string", string>, Match.With<"number", number>]>
>
]
>;
```
### Make querySelector typesafe
[Run this as a TypeScript Playground](https://www.typescriptlang.org/play?#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-lIoUou1iqUlaPuhWE72k-7DNVUwMs51tKahxLh-qRuCpq1x4VXJPO12y+UfL3ErP0FaMGAyMA8TwsbxJfz4IL2KAacIAXkF8xoLA01zaAtt62tBTkJlLqHXYHYwBgqkIRAsq7j6l4u55BQAMmgYKfKoUN2Ht3Jd-vD+tCCe1+fL9v1AgABVfgRH4B8znXTdzFfd8Dw6BwOkiOAOk6ZCOgKJCog6ABiDofzPC8lG3ABBA8egIx8CgAWWQGAKGIVQlw+ONaPo4gCgAdX3RiAGsWBkCBsEwdRqOvftBxgdRkDMHZkG8WiwGuQoAHkACMACtlG3ABxFgD0KAB9ZTRPErwfGk2T5JYRSLEoljBTYhiuJ41RkH4GQTLEiSfAsAV+j8gLGHoChRGMKoeR6OBp0kaR5DsEIoCsDoEA6FwAG56AAeiyliAD0TlC-hwu4VAAEZookKRZFHRLkrANLMpy-LCrC+BSoAJkq2KaoSlQko6JhgCWAoODQVA5O8Rrstyj4CpCtqItQABmbrqvi4J+uSoaljgcJkGm5q5ta4r2p5AAWNa4tqraOjANo6JMfpDtmyp5qKkqeQAViu3rNugbbhrgMACj0XQUDaYhuGwSdCBwwhnoymaWoW06loANl+jax2SnDgCYF6UY+s7UAAdixm6AcG4aHpgJ6HGINArDAPa4FDUQzBcQnjtRz7UAADgpvqqfpVArB22mnuuMAuaRo63pOvmAE4hf+gaJceqB+mlyWtYZpmWfCdnzFlprXoqd7FtKsqopi9bKfVoG3kZsXkFZ0WrDU64KBcWXkZ54L6CAA)
```ts
import * as H from 'hotscript'
declare function querySelector<T extends string>(selector: T): ElementFromSelector<T> | null
interface Trim extends H.Fn {
return:
this["arg0"] extends `${infer Prev} ,${infer Next}` ?
H.
lt;Trim, `${Prev},${Next}`> :
this["arg0"] extends `${infer Prev}, ${infer Next}` ?
H.lt;Trim, `${Prev},${Next}`> :
this["arg0"] extends `${infer Prev}:is(${infer El})${infer Rest}` ?
H.lt;Trim, `${Prev}${El}${Rest}`> :
this["arg0"] extends `${infer Prev}:where(${infer El})${infer Rest}` ?
H.lt;Trim, `${Prev}${El}${Rest}`> :
this["arg0"] extends `${infer El}(${string})${infer Rest}` ?
H.lt;Trim, `${El}${Rest}`> :
this["arg0"] extends `${infer El}[${string}]${infer Rest}` ?
H.lt;Trim, `${El}${Rest}`> :
this["arg0"]
}
type ElementFromSelector<T> = H.Pipe<T, [
Trim,
H.Strings.Split<' '>,
H.Tuples.Last,
H.Strings.Split<','>,
H.Tuples.ToUnion,
H.Strings.Split<":" | "[" | "." | "#">,
H.Tuples.At<0>,
H.Match<[
H.Match.With<keyof HTMLElementTagNameMap, H.Objects.Get<H._, HTMLElementTagNameMap>>,
H.Match.With<any, HTMLElement>
]>
]>
```
