@bussin/list-comprehensions

A strongly typed list comprehension library built with TypeScript. Uses deferred execution for more performant operations. Provides prototype extensions on all Iterable<T> NodeJS classes for more fluent use (Array, Map, Set, etc., this is strictly opt-in). Inspired by LINQ.

License: MIT

Installation

npm install @bussin/list-comprehensions

Quick Start

// Extend the `Array<T>` prototype (optional)
import '@bussin/list-comprehensions/extensions/Array';

const numbers = [1, 2, 3, 4, 5];

// The `where` and `select` methods build up a query but don't run until you call `toArray()` (deferred execution).
const result = numbers
  .where(n => n > 2)       // Filters numbers greater than 2
  .select(n => n * n)      // Squares each remaining number
  .toArray();              // Materializes the result

console.log(result); // [9, 16, 25]

console.log(results.any(n => n > 100)) // false
console.log(results.all(n => n > 0)) // true

Without extending the Array prototype:

import { Enumerable } from '@bussin/list-comprehensions';

const people = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 20 },
  { name: 'Carol', age: 30 },
  { name: 'David', age: 15 },
];

const namesOfAdults = Enumerable
  .from(people)                      // Converts Array<People> to Enumerable<People>
  .where(person => person.age >= 18) // Filters people older than 18
  .select(person => person.name)     // Selects the persons' name
  .toArray();                        // Materializes the result

console.log(namesOfAdults); // ['Alice', 'Bob', 'Carol']

const youngest = Enumerable
  .from(people)                 // Converts Array<People> to Enumerable<People>
  .minBy(person => person.age); // Gets the youngest person

console.log(youngest.name); // 'David'

Methods

(work in progress)

• [ ] aggregate
• [ ] aggregateBy
• [x] all
• [x] any
• [x] append
• [ ] asEnumerable
• [ ] average
• [ ] cast
• [x] chunk
• [x] concat
• [x] contains
• [x] count
• [x] countBy
• [ ] defaultIfEmpty
• [ ] distinct
• [ ] distinctBy
• [ ] elementAt
• [ ] elementAtOrDefault
• [ ] empty
• [ ] except
• [ ] exceptBy
• [ ] first
• [ ] firstOrDefault
• [ ] groupBy
• [ ] groupJoin
• [ ] index
• [ ] intersect
• [ ] intersectBy
• [ ] join
• [ ] last
• [ ] lastOrDefault
• [ ] longCount
• [ ] max
• [ ] maxBy
• [ ] min
• [x] minBy
• [ ] ofType
• [ ] order
• [ ] orderBy
• [ ] orderByDescending
• [ ] orderDescending
• [ ] prepend
• [x] range
• [x] repeat
• [x] reverse
• [x] select
• [x] selectMany
• [ ] sequenceEqual
• [ ] single
• [ ] singleOrDefault
• [x] skip
• [ ] skipLast
• [ ] skipWhile
• [ ] sum
• [x] take
• [ ] takeLast
• [ ] takeWhile
• [ ] thenBy
• [ ] thenByDescending
• [ ] toArray
• [ ] toList
• [ ] toLookup
• [ ] toMap
• [x] toRecord
• [ ] toSet
• [ ] tryGetNonEnumeratedCount
• [ ] union
• [ ] unionBy
• [x] where
• [ ] zip

Support

Please create a PR if you find any missing functionality that you's like to add. For bugs, please use the issues tracker. I'll be happy to help you!