array-fp-utils

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.14+

API

• groupBy
• intersect
• intersectWith
• isDistinctArray
• 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

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

Causaly is building the world's largest biomedical knowledge platform, using technologies such as TypeScript, React and Node.js. Find out more about our openings at https://apply.workable.com/causaly/.

License

MIT

Changelog

0.2.0

Minor Changes

• 58e76d4: Mark input args as Readonly since functions are pure.