ts-array-extensions

A library that provides common array transformation functions beyond the built in ones in js, e.g. map, filter. See functions

Inspired by swift and LINQ.

Install

Use your package manager of choice, e.g.

npm i ts-array-extensions

Using

There are three modes for consuming the functions from this library.

• extending Array.prototype using a utility import (simplest - recommended).
• importing the functions directly (cleanest).
• or using the pipe() function (compromise, one eye on the future).

1. Extend Array.prototype

Add a utility import in an entry point file.

// entry-point.ts
import 'ts-array-extensions/apply';

// some-other-file.ts
[1, 2, 3]
  .compactMap(v => {
    if (v % 2 !== 0) return v;
  })
  .cume(); // [1, 4]

Or individual utility imports for only the functions that you need. The rest can be shaken out of the tree by a bundler.

// entry-point.ts
import 'ts-array-extensions/apply/compactMap';
import 'ts-array-extensions/apply/cume';

The imports are idempotent. Mistaken (or necessary) duplicate imports will have no adverse effects.

2. Importing the functions directly

Just import the functions directly and use them as you need them.

This is the cleanest approach with no prototype pollution, but readability is sacrificed when wanting to chain multiple functions - or more accurately nest - as it has to be in this mode.

import { cume, compactMap } from 'ts-array-extensions';

cume(
  compactMap(
    [1, 2, 3],
    v => {
      if (v % 2 !== 0) return v;
    }
  )
); // [1, 4]

3. Use pipe() utility function

Almost as clear as the prototype extension mode, but without the prototype pollution.

import { pipe, cume, compactMap } from 'ts-array-extensions/pipes';

pipe(
  [1, 2, 3],
  compactMap(v => {
    if (v % 2 !== 0) return v;
  }),
  cume()
) // [1, 4]

This is ready for when the pipeline operator proposal lands in typescript

// DO NOT USE (yet)
// awaiting https://github.com/tc39/proposal-pipeline-operator

import { cume, compactMap } from 'ts-array-extensions/pipes';

[1, 2, 3]
  |> compactMap(v => {
    if (v % 2 !== 0) return v;
  })
  |> cume() // [1, 4]

Available Functions

The following examples use the Array.prototype extension mode, but can also be used with the direct import and pipe modes.

• any
• compact
• compactMap
• cume
• distinct
• except
• first
• groupBy
• innerJoin
• interleave
• leftJoin
• max
• min
• none
• outerJoin
• sortBy
• sum
• toRecord
• union

any

Returns true if the array contains any elements.

[1, 2, 3].any(); // true

[].any(); // false

compact

Returns elements of the array that are not null or undefined.

[1, null, 2].compact(); // [1, 2]

compactMap

Maps elements and returns results that are not null or undefined.

[1, 2, 3].compactMap(v => {
  if (v % 2 !== 0) return v;
}); // [1, 3]

cume

Returns the a running total of all the elements in the array, optionally mapping them first with a callback

[1, 10, 100].cume(); // [1, 11, 111]

[1, 10, 100].cume(v => v * 10); // [10, 110, 1110]

distinct

Returns elements of the array that are unique, using a comparer function if supplied, or === if not.

[1, 1, 2, 2].distinct(); // [1, 2]

[
  { day: 1, month: 1, year: 1979 },
  { day: 1, month: 1, year: 1979 },
  { day: 2, month: 1, year: 1979 },
  { day: 2, month: 1, year: 1979 }
].distinct(
  (a, b) => a.day === b.day
    && a.month === b.month
    && a.year === b.year
);
// [
//   { day: 1, month: 1, year: 1979 },
//   { day: 2, month: 1, year: 1979 }
// ]

except

Returns values from the first array, that aren't present in the second, using a comparer function if supplied, or === if not.

[1, 2, 3].except([2, 3, 4]); // [1]

[
  { day: 1, month: 1, year: 1979 },
  { day: 2, month: 1, year: 1979 }
].except(
  [
    { day: 2, month: 1, year: 1979 },
    { day: 3, month: 1, year: 1979 }
  ],
  (a, b) => a.day === b.day
    && a.month === b.month
    && a.year === b.year
);
// [
//   { day: 1, month: 1, year: 1979 }
// ]

first

Returns the first element of the array or null if empty.

['morning', 'afternoon'].first(); // 'morning'

groupBy

Returns an array of Group<K, V> extracted from the array using a callback, and an optional key comparer.

[
  { make: 'Ford', model: 'Fiesta' },
  { make: 'Ford', model: 'Focus' },
  { make: 'Vauxhall', model: 'Corsa' },
  { make: 'Vauxhall', model: 'Astra' }
].groupBy(k => k.make);
// [
//   {
//     key: 'Ford',
//     values: [
//       { make: 'Ford', model: 'Fiesta' },
//       { make: 'Ford', model: 'Focus' }
//     ]
//   },
//   {
//     key: 'Vauxhall',
//     values: [
//       { make: 'Vauxhall', model: 'Corsa' },
//       { make: 'Vauxhall', model: 'Astra' }
//     ]
//   }
// ]

innerJoin

Matches two array using a callback and returns the joined results.

const leftData = [
  { id: 1, name: 'Apples', groupId: 1 },
  { id: 2, name: 'Oranges', groupId: 1 },
  { id: 3, name: 'Cornflakes', groupId: 2 },
  { id: 4, name: 'Random', groupId: null }
];
const rightData = [
  { id: 1, name: 'Produce' },
  { id: 2, name: 'Grocery' },
  { id: 3, name: 'Confectionary' }
];

leftData.innerJoin(rightData, (l, r) => l.groupId === r.id);
// [
//   {
//     left: { id: 1, name: 'Apples', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 2, name: 'Oranges', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 3, name: 'Cornflakes', groupId: 2 },
//     right: { id: 2, name: 'Grocery' }
//   }
// ];

interleave

Adds new elements in between each element of an array.

['one', 'two', 'three'].interleave(() => 'and');
// ['one', 'and', 'two', 'and', 'three']

leftJoin

Matches two array using a callback and returns the joined results and unmatched results from the left array.

const leftData = [
  { id: 1, name: 'Apples', groupId: 1 },
  { id: 2, name: 'Oranges', groupId: 1 },
  { id: 3, name: 'Cornflakes', groupId: 2 },
  { id: 4, name: 'Random', groupId: null }
];
const rightData = [
  { id: 1, name: 'Produce' },
  { id: 2, name: 'Grocery' },
  { id: 3, name: 'Confectionary' }
];

leftData.leftJoin(rightData, (l, r) => l.groupId === r.id);
// [
//   {
//     left: { id: 1, name: 'Apples', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 2, name: 'Oranges', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 3, name: 'Cornflakes', groupId: 2 },
//     right: { id: 2, name: 'Grocery' }
//   },
//   {
//     left: { id: 4, name: 'Random', groupId: null },
//     right: null
//   }
// ];

max

Returns the highest element in the array

[-10, 0, 10].max(); // 10

['a', 'b', 'c'].max(); // 'c'

[].max(); // null

min

Returns the lowest element in the array

[-10, 0, 10].min(); // -10

['a', 'b', 'c'].min(); // 'a'

[].min(); // null

none

Returns false if the array contains any elements.

[1, 2, 3].none(); // false

[].none(); // true

outerJoin

Matches two array using a callback and returns the joined results and unmatched results from both arrays.

const leftData = [
  { id: 1, name: 'Apples', groupId: 1 },
  { id: 2, name: 'Oranges', groupId: 1 },
  { id: 3, name: 'Cornflakes', groupId: 2 },
  { id: 4, name: 'Random', groupId: null }
];
const rightData = [
  { id: 1, name: 'Produce' },
  { id: 2, name: 'Grocery' },
  { id: 3, name: 'Confectionary' }
];

leftData.outerJoin(rightData, (l, r) => l.groupId === r.id);
// [
//   {
//     left: { id: 1, name: 'Apples', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 2, name: 'Oranges', groupId: 1 },
//     right: { id: 1, name: 'Produce' }
//   },
//   {
//     left: { id: 3, name: 'Cornflakes', groupId: 2 },
//     right: { id: 2, name: 'Grocery' }
//   },
//   {
//     left: { id: 4, name: 'Random', groupId: null },
//     right: null
//   },
//   {
//     left: null,
//     right: { id: 3, name: 'Confectionary' }
//   }
// ];

sortBy

Returns a new array, sorted by the result of a callback function.

[
  { name: 'Brian' },
  { name: 'Albert' },
  { name: 'Charlie' }
].sortBy(v => v.name);
// [
//   { name: 'Albert' },
//   { name: 'Brian' },
//   { name: 'Charlie' }
// ]

sum

Returns the total of all the elements in the array, optionally mapping them first with a callback

[1, 10, 100].sum(); // 111

[1, 2, 3, 4].sum(v => v % 2); // 2

toRecord

Returns a Record<K, V> extracted from the array using callbacks.

Similar in functionality to groupBy, but returns a Record, and the last value with a matching key wins

[
  { name: 'Chloe', age: 23 },
  { name: 'Daniel', age: 20 },
  { name: 'Polly', age: 16 },
  { name: 'Lottie', age: 14 },
  { name: 'Theodore', age: 12 },
  { name: 'Hugo', age: 2 }
].toRecord(
  k => k.name,
  v => v.age
);
// {
//   Chloe: 23,
//   Daniel: 20,
//   Polly: 16,
//   Lottie: 14,
//   Theodore: 12,
//   Hugo: 2
// }

union

Returns only the values present in both arrays, using a comparer function if supplied, or === if not.

[1, 2, 3].union([2, 3, 4]); // [2, 3]

[
  { day: 1, month: 1, year: 1979 },
  { day: 2, month: 1, year: 1979 }
].union(
  [
    { day: 2, month: 1, year: 1979 },
    { day: 3, month: 1, year: 1979 }
  ],
  (a, b) => a.day === b.day
    && a.month === b.month
    && a.year === b.year
);
// [
//   { day: 2, month: 1, year: 1979 }
// ]

Contributing

Contributions welcome!