linq.js

A javascript library which adds C# LINQ inspired helper methods for iterators. Supported in Node.js and web browsers.

1import Linq from "linq";
2
3interface User {
4  id: string;
5  firstName: string;
6  lastName: string;
7  city: string;
8  age: number;
9}
10
11const users: User[] = loadUsers();
12const query = Linq(users)
13  .where(v => v.age >= 20 && v.age <= 50)
14  .orderBy('lastName')
15  .then('firstName')
16  .groupBy('city');
17
18for (let group of query) {
19  let i = 0;
20  for (let { firstName, lastName } of group) {
21    console.log("%s %s lives in %s!", firstName, lastName, group.key)
22    i++;
23  }
24
25  console.log("%s people between 20 and 50 live in %s", i, group.key);
26}

Features

• Support for async iterables and promises

1declare const asyncIterable: AsyncIterable<string>;
2var startsWithA = await Linq(asyncIterable).where(v => v.startsWith("A")).toArray();

• Performance enhanced implementations for Arrays, TypedArrays, Maps and Sets

1declare const numbers: number[] = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
2numbers[Symbol.iterator] = () => throw new Error("This should not be called!");
3// gets the length property instead of iterating
4var count = Linq(numbers).select(v => -v).count();
5// gets the last element in the array without iterating all values
6var last = Linq(numbers).last();

• Simplified syntax using property keys

1//select a single property value:
2var names = Linq(users).select(v => v.firstName).toArray();
3//or
4var names = Linq(users).select("firstName").toArray();
5
6//select an object with multiple properties:
7var names = Linq(users).select(({ firstName, lastName }) => ({ firstName, lastName })).toArray();
8//or
9var names = Linq(users).select(["firstName", "lastName"]).toArray();
10
11//filter based on a property
12var names = Linq(users).where(v => v.isActive).toArray();
13//or
14var names = Linq(users).where("isActive").toArray();

• Support for JavaScript collections

1var array: User[] = Linq(users).toArray();
2var set: Set<User> = Linq(users).toSet();
3var map: Map<string, User> = Linq(users).toMap(({ firstName, lastName }) => firstName + " " + lastName);
4var obj: Record<string, User> = Linq(users).toObject("id");

• Static functions for creating sequences

1Linq.range(1, 10).toArray();
2// [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
3Linq.range(0, 4, 5).toArray();
4// [ 0, 5, 10, 15 ]
5Linq.repeat("test", 3).toArray();
6// [ 'test', 'test', 'test' ]

Importing

LinqJS is built in both ESM and UMD formats.

Node.JS (ESM)

1import Linq from "@daniel.pickett/linq-js";

Node.JS (UMD)

1const Linq = require("node_modules/@daniel.pickett/linq-js/lib/index.cjs");

Browser (ESM)

1<script type="module">
2	import Linq from "./node_modules/@daniel.pickett/linq-js/lib/index.mjs";
3
4	let sum = Linq([1,2,3,4,5]).sum();
5	console.log({ sum });
6</script>

Browser (UMD)

1<script type="text/javascript" src="/node_modules/requirejs/require.js"></script>
2<script type="text/javascript" src="/node_modules/@daniel.pickett/linq-js/lib/index.cjs"></script>
3<script type="text/javascript">
4	const Linq = require("linq-js");
5	const sum = Linq([1,2,3,4,5]).sum();
6	console.log({ sum });
7</script>