TSLinq

Details

TSLinq is an ES5 compatible port of .NET's LINQ library which tries to be as true to the original as possible.

TSLinq utilises lazily evaluated Enumerable<T>'s, rather than eager evaluation found in other libraries. In addition, it supports ES6 generators allowing for powerful data manipulation.

Ships with a fully functional implementation of Dictionary<TKey, TValue>() which supports collision handling, proper identity hashing by default and custom equality comparers.

Install

npm install tslinq

Usage

import { Enumerable } from 'tslinq'

let things = Enumerable.Of([1, 2, 3])
    .Select(a => a + 2)
    .Where(a => a < 5)
    .Distinct()
    .ToArray();
    
console.log(things);

// Outputs [ 3, 4 ]

Using ES6 generator functions

function* GetNumbers() {
    let i = 0;
    while(true) {
        yield i++;
    }
}

let FirstTenNumbers = Enumerable.Of(GetNumbers)
    .Take(10)
    .ToArray();
    
console.log(FirstTenNumbers);

// Outputs [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

Using manually created generator functions

let i = 0;
const generator = () => {
    return {
        next: function () {
            if (i >= 3) {
                throw new Error('Generator should not be invoked when the enumerable hasn\'t been materialized');
            }
            return { done: false, value: i++ };
        }
    };
};

const result =
    Enumerable.Of(generator)
        .Take(3)
        .ToArray();

console.log(result);

// Outputs [ 0, 1, 2 ]

Using Dictionary<TKey, TValue>

Basic implementation

const objectA: any = {};
const objectB: any = {};

const dictionary = new Dictionary<any, number>();
dictionary.Add(objectA, 5);
dictionary.Add(objectB, 10);

dictionary.Get(objectA); // Returns 5
dictionary.Get(objectB); // Returns 10

Using a custom equality comparer

const objectA: any = {};
const objectB: any = {};

const equalityComparer = {
    Equals: (left: any, right: any) => true,
    GetHashCode: (item: any) => JSON.stringify(item)
};

const dictionary = new Dictionary<any, number>(equalityComparer);
dictionary.Add(objectA, 5);
dictionary.Add(objectB, 10); // Throws an exception, key already exists, as the JSON strings match, 
                             // and we always return true when comparing

const objectA: any = {};
const objectB: any = {};

const equalityComparer = {
    Equals: (left: any, right: any) => left === right,
    GetHashCode: (item: any) => JSON.stringify(item)
};

const dictionary = new Dictionary<any, number>(equalityComparer);
dictionary.Add(objectA, 5);
dictionary.Add(objectB, 10); // Does not throw - collisions are properly handled,
                             // And we then check for identity equality