ttuple

Array wrapper to make methods stricter

It's recommended to enable noPropertyAccessFromIndexSignature option to see the difference

How to use

Creates tuples

import { toTuple } from "ttuple";

class Segment {
  public bitrate: number = -1;
}

// ❌ Without ttuple

const arraySegments = [new Segment()];

arraySegments;
// ^? const arraySegments: Segment[]

// ✅ With ttuple

const tupleSegments = toTuple([new Segment()]);

tupleSegments;
// ^? const tupleSegments: [Segment]

Playground – https://tsplay.dev/NlE5Om 🏝

Iterates over array and saves tuple type

import { map } from "ttuple";

class Segment {
  public bitrate: number = -1;
}

// ❌ Without ttuple

const segments: [Segment] = [new Segment()];

const arrayBitrates = segments.map((segment) => segment.bitrate);

arrayBitrates;
// ^? const arrayBitrates = number[]

// ✅ With ttuple

const tupleBitrates = map((segment) => segment.bitrate, [new Segment()]);

tupleBitrates;
// ^? const tupleBitrates = [number]

Playground – https://tsplay.dev/wRG2EN 🏝

Checks array length and returns array element

import { first, length } from "ttuple";

class Segment {
  public bitrate: number = -1;
}

const segments: Segment[] = [];

// ❌ Without ttuple

if (segments.length < 1) {
  throw new Error("Missing segment element");
}

const arrayFirstSegment = segments[0];

arrayFirstSegment;
// ^? const arrayFirstSegment: Segment | undefined

// ✅ With ttuple

if (!length(segments, ">= 1")) {
  throw new Error("Missing segment element");
}

const tupleFirstSegment = first(segments);

tupleFirstSegment;
// ^? const tupleFirstSegment: Segment

Playground – https://tsplay.dev/NV4pxW 🏝

import { length, last } from "ttuple";

class Segment {
  public bitrate: number = -1;
}

const segments: Segment[] = [];

// ❌ Without ttuple

if (segments.length < 1) {
  throw new Error("Missing segment element");
}

const arrayLastSegment = segments[segments.length - 1];

arrayLastSegment;
// ^? const arrayLastSegment: Segment | undefined

// ✅ With ttuple

if (!length(segments, ">= 1")) {
  throw new Error("Missing segment element");
}

const tupleLastSegment = last(segments);

tupleLastSegment;
// ^? const tupleLastSegment: Segment

Playground – https://tsplay.dev/WoaEpN 🏝

API

declare const toTuple: <T extends AnyArray>(array: [...T]) => T;

declare const at: <N extends number>(
  index: N
) => <T extends AnyArray>(array: [...T]) => At<T, `${N}`>;

declare const first: <T extends AnyArray>(array: [...T]) => At<T, "0">;
declare const second: <T extends AnyArray>(array: [...T]) => At<T, "1">;
declare const secondToLast: <T extends AnyArray>(array: [...T]) => At<T, "-2">;
declare const last: <T extends AnyArray>(array: [...T]) => At<T, "-1">;

declare const map: <T extends AnyArray, U>(
  callback: (value: ElementOf<T>, index: number) => U,
  array: [...T]
) => Map<T, U>;

declare function length<
  T extends AnyArray,
  S extends `${number}`,
  R = ToTuple<ElementOf<T>, S>
>(array: T, condition: `>= ${S}`): array is R extends T ? R : never;

Supported methods

• length (with >= comparator)
• map
• at