array-fp-utils

Array utilities for functional programming in TypeScript.

Features

• Battle tested performance;
• Meant to be used with a proper FP library, such as fp-ts;
• Extensive tests.

Installation

npm install array-fp-utils

Requirements

• Node.js v.16+

API

• groupBy
• intersect
• intersectWith
• isDistinctArray
• isSameValueSet
• isSameValueSetWith
• isSubsetOf
• isSubsetOfWith
• unique
• uniqueBy

groupBy

import { pipe } from 'fp-ts/lib/function';
import { groupBy } from 'array-fp-utils';

const arr = [
  {
    key: 2,
    score: 2,
  },
  {
    key: 1,
    score: 0.5,
  },
  {
    key: 1,
    score: 1,
  },
];

// group by key, while maintaining array item order
const groupedArr = pipe(
  arr,
  groupBy((item) => item.key)
);

// groupedArr now contains the following
// [
//   [
//     {
//       "key": 2,
//       "score": 2,
//     },
//   ],
//   [
//     {
//       "key": 1,
//       "score": 0.5,
//     },
//     {
//       "key": 1,
//       "score": 1,
//     },
//   ],
// ]

intersect

import { pipe } from 'fp-ts/lib/function';
import { intersect } from 'array-fp-utils';

const arr = ['a', 'b', 'c', 'd', 'e'];
const otherArr = ['b', 'c', 'f'];

// calculates the intersection of two arrays
const intersection = pipe(arr, intersect(otherArr)); // returns ['b', 'c']

intersectWith

import { pipe } from 'fp-ts/lib/function';
import { intersectWith } from 'array-fp-utils';

const arr = [
  { foo: 'a' },
  { foo: 'b' },
  { foo: 'c' },
  { foo: 'd' },
  { foo: 'e' },
];

const otherArr = [{ bar: 'b' }, { bar: 'c' }, { bar: 'f' }];

// calculate the intersection of two arrays using comparator function
const arr = pipe(
  mockData,
  intersectWith(otherArr, (item, otherItem) => item.foo === otherItem.bar)
);

// arr = [{ foo: 'b' }, { foo: 'c' }]

isDistinctArray

import { pipe } from 'fp-ts/lib/function';
import { isDistinctArray } from 'array-fp-utils';

pipe([1, 2, 3], isDistinctArray); // returns true
pipe([1, 1, 2, 3], isDistinctArray); // returns false

isSameValueSet

Indicates whether an array contains the same set of items with another array, irrelevant of position (sorting).

Note: only accepts arrays of primitive values.

Example

import { pipe } from 'fp-ts/lib/function';
import { isSameValueSet } from 'array-fp-utils';

pipe([1, 2, 3], isSameValueSet([3, 2, 1])); // returns true

pipe([1, 2], isSameValueSet([1, 2, 3])); // returns false
pipe([1, 2, 3], isSameValueSet([1, 2, 4])); // returns false

isSameValueSetWith

Indicates whether an array contains the same set of items with another array, irrelevant of position (sorting), using a comparator function.

Example

import { pipe } from 'fp-ts/lib/function';
import { isSameValueSetWith } from 'array-fp-utils';

pipe(
  [{ key: 1 }, { key: 2 }, { key: 3 }],
  isSameValueSetWith([3, 2, 1], (value, otherValue) => value.key === otherValue)
); // returns true

isSubsetOf

import { pipe } from 'fp-ts/lib/function';
import { isSubsetOf } from 'array-fp-utils';

const arr = ['a', 'b', 'c', 'd'];

const isSubset = pipe(['b', 'd'], isSubsetOf(arr)); // returns true
const isSubset = pipe(['a', 'e'], isSubsetOf(arr)); // returns false

isSubsetOfWith

import { pipe } from 'fp-ts/lib/function';
import { isSubsetOfWith } from 'array-fp-utils';

const arr = [
  { foo: 'a' },
  { foo: 'b' },
  { foo: 'c' },
  { foo: 'd' },
  { foo: 'e' },
];
const otherArr = [{ bar: 'b' }, { bar: 'c' }, { bar: 'f' }];

const isSubset = pipe(
  arr,
  isSubsetOfWith(otherArr, (item, otherItem) => item.foo === otherItem.bar)
); // returns false since "f" does not exist in arr

unique

import { pipe } from 'fp-ts/lib/function';
import { unique } from 'array-fp-utils';

const countries = [
  'Greece',
  'Greece',
  'Greece',
  'United States',
  'United Kingdom'
  'United States',
];

// returns ['Greece', 'United Kingdom', 'United State']
const uniqueArray = pipe(countries, unique);

uniqueBy

import { pipe } from 'fp-ts/lib/function';
import { uniqueBy } from 'array-fp-utils';

const users = [
  {
    id: 1,
    name: 'John'
  },
  {
    id: 2,
    name: 'Michael'
  }
  {
    id: 3,
    name: 'Michael'
  }
]

// removes duplicate values from array in FiFo
// returns [{id:1, name: 'John'}, {id:2, name: 'Michael'}]
const uniqueArray = pipe(
  users,
  uniqueBy((user) => user.name)
)

Motivation

This library is a collection of array utils, written with FP principles. They focus on performance instead of compatibility.

The alternative would be to use a library like lodash. However, lodash in an attempt to be backwards compatible with older browsers, falls behind on performance. In addition, lodash/groupBy changes the initial order of the array items.

Contribute

Source code contributions are most welcome. Please open a PR, ensure the linter is satisfied and all tests pass.

We are hiring

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License

MIT