Array Method Extensions

This package provides a set of useful methods to extend the functionality of the Array class in TypeScript.

Using these methods, you can easily group, map, distinct, merge, and sum arrays. It reduces code complexity and makes your code more readable.

Index

• Installation
• Usage
• Methods
  • distinctBy
  • equals
  • groupBy
  • mapBy
  • mergeBy
  • sum

Installation

Using Yarn

yarn add @codura/array-method-extension

Using npm

npm install @codura/array-method-extension

Usage

export * from '@codura/array-method-extension';

Methods

distinctBy

Remove duplicates from an Array using a key function

const usersWithDuplicates = [
  { id: '1', gender: 'male', name: 'John' },
  { id: '2', gender: 'female', name: 'Jane' },
  { id: '1', gender: 'male', name: 'John' },
];
const usersWithoutDuplicates = usersWithDuplicates.distinctBy(user => user.id); // [{ id: '1', gender: 'male', name: 'John' }, { id: '2', gender: 'female', name: 'Jane' }]

Remove duplicates from an Array using a key function and a value function

const usersWithDuplicates = [
  { id: '1', gender: 'male', name: 'John' },
  { id: '2', gender: 'female', name: 'Jane' },
  { id: '1', gender: 'male', name: 'John' },
];
const namesWithoutDuplicates = usersWithDuplicates.distinctBy(user => user.id, user => user.name); // ['John', 'Jane']

Check if two arrays, containing decimals, are equal using decimal.js

import Decimal from 'decimal.js';

const decimals1 = [
  new Decimal(23.56457),
  new Decimal(12.34543),
  new Decimal(34.12345),
];
const decimals2 = [
  new Decimal(12.34543),
  new Decimal(23.56457),
  new Decimal(34.12345),
];
const areEqual = decimals1.equals(decimals2); // true

equals

Check if two arrays, containing custom comparable objects, are equal

class ComparableItem {
  constructor(readonly item: string) {
  }

  equals(comparableItem: ComparableItem) {
    return this.item === comparableItem.item;
  }
}

const comparableItems1 = [new ComparableItem('a'), new ComparableItem('b')];
const comparableItems2 = [new ComparableItem('b'), new ComparableItem('a')];
const areEqual = comparableItems1.equals(comparableItems2); // true

Check if two arrays, containing decimals, are equal using decimal.js

import Decimal from 'decimal.js';

const decimals1 = [
  new Decimal(23.56457),
  new Decimal(12.34543),
  new Decimal(34.12345),
];
const decimals2 = [
  new Decimal(12.34543),
  new Decimal(23.56457),
  new Decimal(34.12345),
];
const areEqual = decimals1.equals(decimals2); // true

groupBy

Group an Array to a Map using a key function

const users = [
  { id: '1', gender: 'male', name: 'John' },
  { id: '2', gender: 'female', name: 'Jane' },
  { id: '3', gender: 'male', name: 'Joe' },
];
const usersByGroup = users.groupBy(user => user.gender); // Map([['male', [{id: '1', gender: 'male', name: 'John'}, {id: '3', gender: 'male', name: 'Joe'}]], ['female', [{id: '2', gender: 'female, name: 'Jane'}]]])

Group an Array to a map using a key function and a value function

const users = [
  { id: '1', gender: 'male', name: 'John' },
  { id: '2', gender: 'female', name: 'Jane' },
  { id: '3', gender: 'male', name: 'Joe' },
];
const userNamesById = users.groupBy(user => user.gender, user => user.name); // Map([['male', ['John', 'Joe']], ['female', ['Jane']]])

mapBy

Map an Array to a map using a key function

const users = [
  { id: '1', name: 'John' },
  { id: '2', name: 'Jane' },
  { id: '3', name: 'Joe' },
];
const usersById = users.mapBy(user => user.id); // Map([['1', {id: '1', gender: 'male', name: 'John'}], ['2', {id: '2', gender: 'female, name: 'Jane'}], ['3', {id: '3', gender: 'male', name: 'Joe'}]])

Map an Array to a map using a key function and a value function

const users = [
  { id: '1', name: 'John' },
  { id: '2', name: 'Jane' },
  { id: '3', name: 'Joe' },
];
const userNamesById = users.mapBy(user => user.id, user => user.name); // Map([['1', 'John'], ['2', 'Jane'], ['3', 'Joe']])

mergeBy

Merge custom mergeable objects in an Array

class Drink {
  constructor(readonly name: string, readonly amount: number) {
  }

  merge(drink: Drink) {
    return new Drink(this.name, this.amount + drink.amount);
  }
}

const drinks = [
  new Drink('beer', 5),
  new Drink('wine', 2),
  new Drink('beer', 3),
];
const sum = drinks.merge(drink => drink.name); // [Drink('beer', 8), Drink('wine', 2)]

sum

Sum custom addable objects in an Array

class Payment {
  constructor(readonly note: string, readonly amount: number) {
  }

  add(payment: Payment) {
    return new Payment(this.note, this.amount + payment.amount);
  }
}

const payments = [
  new Payment('first', 100),
  new Payment('second', 200),
  new Payment('third', 300),
];
const sum = payments.sum(new Payment('sum', 0)); // Payment('sum', 600)

Sum decimals in an Array using decimal.js

import Decimal from 'decimal.js';

const decimals = [
  new Decimal(23.56457),
  new Decimal(12.34543),
  new Decimal(34.12345),
];
const sum = payments.sum(new Decimal(0)); // Decimal(70.03345)