blinq

A strongly-typed TypeScript implementation of Microsoft dotnet's LINQ to Objects using ES6 iterables.

With the advent of javascript iterators and generators, its possible to pipe sequences through a bunch of transformations without materializing collections (arrays) for the intermediate steps. This library attempts to recreate the dotnet linq-to-objects api to provide a number of standard operations on iterable sequences.

The following operations are available, and the user can optionally supply their own EqualityComparer (implementing equals and getHashCode) when using the set-based operations.

aggregate, all, any, append, average, concat, count, defaultIfEmpty, distinctBy, distinct, elementAt, except, firstOrDefault, first, flatten, forEach, fullOuterGroupJoin, fullOuterJoin, groupAdjacent, groupBy, groupJoin, intersect, isSubsetOf, isSupersetOf, join, lastOrDefault, last, leftOuterJoin, maxBy, max, minBy, min, orderBy / orderByDescending / thenBy / thenByDescending, preprend, reverse, selectMany, select, sequenceEqual, singleOrDefault, single, skip, skipWhile, sum, take, takeWhile, toArray, toLookup, toMap, toSet, union, where, zipAll, zip

NPM package can be downloaded here.

documentation

Generated documentation can be found at https://biggyspender.github.io/blinq/

How?

Import blinq ES6 style:

import {
  blinq,
  range,
  empty,
  fromGenerator,
  fromSingleValue,
  repeatGenerate,
  repeat,
  EqualityComparer,
  hashString
} from "blinq";

or nodejs style:

const {
  blinq,
  range,
  empty,
  fromGenerator,
  fromSingleValue,
  repeatGenerate,
  repeat,
  EqualityComparer,
  hashString
} = require("blinq")

Now, just wrap your iterable with a call to blinq(myIterable), and start transforming your data:

const someNumbers = [1, 2, 3, 4];
const squares = blinq(someNumbers).select(n => n * n);
for(let v of squares){
    console.log(v);
}

...or if you'd like an array of your results, you can materialize a blinq query with the .toArray() method:

const someNumbers = range(1, 4);
const squaresBelowTen = someNumbers.select(n => n * n).where(n => n < 10);
const arr = squaresBelowTen.toArray();
console.log(arr);

or even spread your results into an array:

const arr2 = [...squaresBelowTen]

A case-insensitive set, using EqualityComparer

const names = ["zebra", "antelope", "ardvaark", "tortoise", "turtle", "dog", "frog"]
const comparer: EqualityComparer<string> = {
    equals: (a, b) => a.toLowerCase() === b.toLowerCase(),
    getHashCode: (x) => hashString(x.toLowerCase())
}
const set = blinq(names).toSet(comparer)
expect(set.has("DOg")).toBeTruthy()

More examples:

Let's make a collection of cars:

const cars = [{
    manufacturer:"Ford",
    model:"Escort"
  },{
    manufacturer:"Ford",
    model:"Cortina"
  },{
    manufacturer:"Renault",
    model:"Clio"
  },{
    manufacturer:"Vauxhall",
    model:"Corsa"
  },{
    manufacturer:"Ford",
    model:"Fiesta"
  },{
    manufacturer:"Fiat",
    model:"500"
  }
];

...and sort them by manufacturer, and then by model:

const orderedCars = blinq(cars).orderBy(c => c.manufacturer).thenBy(c => c.model);
console.log(orderedCars.toArray());

Or we could count the number of cars for each manufacturer:

const carsPerManufacturer = blinq(cars)
  .groupBy(c => c.manufacturer)
  .select(g => ({
    manufacturer:g.key, 
    count:g.count()
  }))
  .orderBy(c => c.manufacturer);
for(var c of carsPerManufacturer){
  console.log(`${c.manufacturer} : ${c.count}`);
}

What next?

The tests for this project are kept up to date and are the best place to look for other examples.

acknowledgements

Created using the wonderful https://github.com/alexjoverm/typescript-library-starter.