RoyalIcing / itsybitsy

Map, filter, flat map, reduce — all in one place

🕷🕸 itsybitsy

Map, filter, flat map, reduce — all with the one function

Install

npm add itsybitsy

Examples

Map

import { bitsy } from "itsybitsy";

function* toString(n: number) {
  yield n.toString();
}

const numbers = [1, 2, 3];
const strings = [...bitsy(toString).from(numbers)];
// ["1", "2", "3"]

Filter

import { bitsy } from "itsybitsy";

function* whereEven(item: number) {
  if (item % 2 === 0) yield item;
}

const numbers = [1, 2, 3, 4, 5, 6];
const evens = [...bitsy(whereEven).from(numbers)];
// [2, 4, 6]

Reduce

import { bitsy } from "itsybitsy";

function* count(_item: unknown, accum: number) {
  return accum + 1;
}

function* sum(item: number, accum: number) {
  return accum + item;
}

const numbers = [1, 2, 3, 4, 5, 6];
const totalCount = bitsy(count, 0).result(numbers); // 6
const totalSum = bitsy(sum, 0).result(numbers); // 21

Flat map

import { bitsy } from "itsybitsy";

function* repeatEvens(item: number) {
  if (item % 2 === 0) {
    yield item;
    yield item;
  } else {
    yield item;
  }
}

const numbers = [1, 2, 3, 4, 5, 6];
const withEvensRepeated = [...bitsy(repeatEvens).from(numbers)];
// [1, 2, 2, 3, 4, 4, 5, 6, 6]

Compact

import { bitsy } from "itsybitsy";

function* compact<T>(item: T): Generator<Exclude<T, null | undefined | false>> {
  if (item == null || (typeof item === 'boolean' && item === false)) return;
  yield item as Exclude<T, null | undefined | false>;
}

const itemsWithFalsey = [0, 1, false, 2, true, 3, null, 4, undefined, 5];
const itemsWithoutFalsey = [...bitsy(compact).from(itemsWithFalsey)];
// [0, 1, 2, true, 3, 4, 5]

Chunk into pairs

import { bitsy } from "itsybitsy";

function* chunk2(item: string | number, accum: undefined | unknown) {
  if (accum === undefined) {
    return item;
  } else {
    yield [accum, item];
    return;
  }
}

const pairsFlat = [
  "/",
  8,
  "/about",
  3,
  "/docs/api",
  2,
  "/pricing",
  1,
];
const pairs = [...bitsy(chunk2, undefined).from(pairsFlat)];
// [ ["/", 8], ["/about", 3], ["/docs/api", 2], ["/pricing", 1] ]

Chaining with .then

import { bitsy } from "itsybitsy";

function* add1(item: number) {
  yield item + 1;
}

function* toString(item: number) {
  yield item.toString();
}

function* repeatEvens(item: number) {
  if (item % 2 === 0) {
    yield item;
    yield item;
  } else {
    yield item;
  }
}

const numbers = [1, 2, 3, 4, 5];
const strings = [...bitsy(add1).then(repeatEvens).then(toString).from(numbers)];
// ["2", "2", "3", "4", "4", "5", "6", "6"]

---

Alternative name: forte?

const strings = [...forte(addOne).then(toString).of(numbers)];

const totalCount = forte(count, 0).reduce(numbers);

---

Alternative API

bitsy({
  *0(n: number) {
    if (n % 2 === 0) yield n;
  },
  *1(n: number) {
    yield n.toString();
  },
  *2(s: string) {
    yield `#${s}`;
  }
}).from([1, 2, 3, 4, 5, 6]);
// ["#2", "#4", "#6"]