tsdotnet / linq

A familiar set of functions that operate on JavaScript iterables (ES2015+) in a similar way to .NET's LINQ does with enumerables.

Docs

tsdotnet.github.io/linq

Source

GitHub

API

Iterating

for(const e of linq(source)
    .filter(a, b, c)) {
    // Iterate filtered results.
}

for(const e of linq(source)
    .filter(a, b, c)
    .transform(x)) {
    // Iterate filtered and then transformed results.
}

Resolving

const result = linq(source)
    .filter(a, b, c)
    .transform(x)
    .resolve(r);

Examples

`linq<T>` with imported filters

import linq from '@tsdotnet/linq/dist/linq';
import range from '@tsdotnet/linq/dist/iterables/range';
import where from '@tsdotnet/linq/dist/filters/where';
import descending from '@tsdotnet/linq/dist/filters/descending';

const source = range(1,100); // Iterable<number>
const filtered = linq(source).filters(
     where(n => n%2===1),
     descending);

for(const o of filtered) {

    // Emit all odd numbers in descending order.
    console.log(o);  // 99, 97, 95 ...
}

`linqExtended<T>` with simplified imports

import {linqExtended, iterables, resolutions} from '@tsdotnet/linq';

const source = iterables.range(1,100); // Iterable<number>
const result = linqExtended(source)
    .where(n => n%2===1) // odd numbers only
    .resolve(resolutions.sum); // 2500

import {linqExtended} from '@tsdotnet/linq';
import {range} from '@tsdotnet/linq/dist/iterables';
import {sum} from '@tsdotnet/linq/dist/resolutions';

const source = iterables.range(1,100); // Iterable<number>
const result = linqExtended(source)
    .where(n => n%2===1) // odd numbers only
    .resolve(resolutions.sum); // 2500

Concepts

Iterables

ES2015 enables full support for the iteration protocol.

Iterables are a significant leap forward in operating with data sequences. Instead of loading entire sets into arrays or other collections, iterables allow for progressive iteration or synchronous streaming of data.

tsdotnet/linq is designed around iterables but also optimized for arrays.

Generators

Iterable<T> helpers are provided as sources. Calling for an Iterator<T> should always start from the beginning and iterators are not shared. Same behavior as LINQ in .NET.

empty, range, and repeat to name a few. See the docs for a full list.

Filters

linq(source).filter(a, b);
linq(source).filter(a).filter(b);

Any function that receives an Iterable<T> and returns an Iterable<T> is considered an IterableFilter<T>. A filter may result in a different order or ultimately a completely different set than the input but must be of the same type.

There are an extensive set of filters. See the docs for a full list.

Transforms

linq(source).transform(x);
linq(source).filter(a).transform(x);

Any function that receives an Iterable<T> and returns an Iterable<TResult> is considered an IterableValueTransform<T, TResult>.

Any filter can be used as a transform, but not every transform can be used as a filter.

notNull, rows, select, selectMany and groupBy to name a few. See the docs for a full list.

Resolutions

linq(source).resolve(r);
linq(source).transform(x).resolve(r);
linq(source).filter(a, b).transform(x).resolve(r);

A resolution is a transform that takes an Iterable<T> and returns TResult. Unlike .filter(a) and .transform(x), .resolve(r) does not wrap the result in another Linq<T>.

There are an extensive set of resolutions. See the docs for a full list.

History

Originally this was a port of linq.js converted to full TypeScript under the name TypeScript.NET Library and then TypeScript.NET-Core with full module support but potentially more than a user might want for a simple task. Instead of .NET style extensions, Enumerables incurred a heavy cost of all the extensions under one module.

Modern web standards and practices demanded more granular access to classes and functions. Hence tsdotnet was born. tsdotnet/linq functionally allows for all the features of its predecessor as well as providing type-safety, and most of the features of LINQ in .NET while not forcing the consumer to download unneeded/undesired modules (extensions).

Megasware128/linq