LINQ To TypeScript

• Implementation of LINQ for TypeScript
• Targets TypeScript 2.8 and ES 2016

await Enumerable
    .from([bing, google, quackQuackGo])
    .asParallel()
    .selectAsync(downloadHtml)
    .select(getTitle)
    .toArray()

Release	InDev

Getting Started

npm i linq-to-typescript

tsconfig.json

"compilerOptions": {
    "target": "es2016",
    "lib": [
      "dom",
      "es2016",
      "esnext.asynciterable"
    ],
}

• The strict TS option is recommended.
• Library is dependent on core-js for implementation of Symbol.asyncIterator

Using the Library

With Wrappers

// 0. Import Module
import { ArrayEnumerable, Enumerable, AsyncEnumerable, ParallelEnumerable } from "linq-to-typescript"

// To Use With Wrappers
const evenNumbers = Enumerable.from([1, 2, 3, 4, 5, 6, 7, 8, 9]).where((x) => x % 2 === 0).toArray()

Without Wrappers

// 0. Import Module
import { Enumerable, AsyncEnumerable, ParallelEnumerable, initializeLinq } from "linq-to-typescript"
// 1. Declare that the JS types implement the IEnumerable interface
declare global {
    interface Array<T> extends IEnumerable<T> {
        concat(items: IEnumerable<T>): IEnumerable<T>;
        concat(...items: Array<ReadonlyArray<T>>): ArrayEnumerable<T>;
        concat(...items: Array<T | ReadonlyArray<T>>): ArrayEnumerable<T>;    
    }
    interface Uint8Array extends IEnumerable<number> { }
    interface Uint8ClampedArray extends IEnumerable<number> { }
    interface Uint16Array extends IEnumerable<number> { }
    interface Uint32Array extends IEnumerable<number> { }
    interface Int8Array extends IEnumerable<number> { }
    interface Int16Array extends IEnumerable<number> { }
    interface Int32Array extends IEnumerable<number> { }
    interface Float32Array extends IEnumerable<number> { }
    interface Float64Array extends IEnumerable<number> { }
    interface Map<K, V> extends IEnumerable<[K, V]> { }
    interface Set<T> extends IEnumerable<T> { }
}
// 2. Bind Linq Functions to Array and Map
initializeLinq()
// 3. Use without a wrapper type
const evenNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9].where((x) => x % 2 === 0).toArray()

Examples

Please refer to EXAMPLES.md

API

LinqToTypeScript implements the functionality of the IEnumerable interface

• IEnumerable, IAsyncEnumerable, and IParallelEnumerable interfaces are based on,
• IEnumerable<T> Interface
• Some changes made due to conflics with existing method names
• Some changes made due to limitations of JavaScript

IEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IAsyncEnumerable
• Implements Iterable<T> interface

IAsyncEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IAsyncEnumerable
• For asynchronous iteration
• Implements AsyncIterable<T> interface

IParallelEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IParallelEnumerable
• For asynchronous iteration in parallel (where possible)
• Implements AsyncIterable<T> interface.

Shared Instance Methods

* Async methods take an async function

Static Methods

TypeDoc Documentation

Refer to https://arogozine.github.io/linqtotypescript/

Design

Binding new APIs to Array Types

JavaScript doesn't have extension methods like in C#, therefore we extend the class itself with new methods. Call initializeLinq to bind library functions to default Array methods,

The following collections support IEnumerable,

• Array
• Map
• Set
• String
• Int8Array
• Int16Array
• Int32Array
• Uint8Array
• Uint8ClampedArray
• Uint16Array
• Uint32Array
• Float32Array
• Float64Array

Using Wrappers

Wrappers are safer as they won't interfere with other libraries.

// To Create an IEnumerable<T>
Enumerable.from(iterableIteratorOrArray)
// To Create an IAsyncEnumerable<T>
AsyncEnumerable.from(asyncIterableIteratorOrPromiseArray)
// To Create an IParallelEnumerable<T>
ParallelEnumerable.from(arrayOfPromises)

The root classes are

• Enumerable
• AsyncEnumerable
• ParallelEnumerable

Collections simply call the static methods defined on these base types.

F.A.Q.

Q I am getting a Cannot find module 'core-js/modules/es7.symbol.async-iterator'

A Ensure you have core-js NPM package installed.

Q Why did you create this?

A For fun and to gain understanding of TypeScript and Node Package Manager.

Q Why not target ES5?

A ES5 doesn't have iterators and generators which this library relies on to mimic the lazy nature of IEnumerable. You are free to target ES5 instead.

Q How does this compare to other LINQ libraries?

A They are more mature, but not made targeting latest ECMAScript features.

Q Why should I use this instead of lodash or something similar?

A

• TypeScript first. Libraries which target JavaScript first do additional type checking which can have a negative impact on performance.
• This library uses iterators and generators. These are new language features which have no support in legacy browsers like IE11.

Q Which browsers are supported?

A Firefox, Chrome, and Edge. IE is not supported.

Q Can I contribute?

A Please do!