queryable-ts

A C# Linq-like fluent interface for array manipulation in TypeScript.

Note: This project is a proof of concept created by a student for learning purposes. It is not intended for production use.

Description

queryable-ts provides a Queryable class that wraps an array and allows for chaining multiple data manipulation methods in a style similar to C#'s LINQ. This allows for more readable and expressive queries on collections.

Features

• Fluent, chainable API.
• Lazy evaluation is not implemented; the query is executed when a terminal method like .all() is called.
• Methods for filtering, projecting, sorting, and element selection.
• Strongly typed to leverage TypeScript's static analysis.

Usage

First, import the Queryable class and instantiate it with your array.

import { Queryable } from './lib/queryable';

const people = [
	{ name: 'Alice', age: 30 },
	{ name: 'Bob', age: 25 },
	{ name: 'Charlie', age: 35 },
	{ name: 'David', age: 25 },
];

// Create a query
const query = new Queryable(people);

// Chain methods to transform the data
const namesOfPeopleOver25 = query
	.where((person) => person.age > 25)
	.sortByAsc('name')
	.select((person) => person.name)
	.all(); // Execute the query and get the results

console.log(namesOfPeopleOver25); // Output: ['Alice', 'Charlie']

API

The Queryable class implements the following methods:

Selectors

• select<K>(cb): Projects each element of a sequence into a new form.
• where(cb): Filters a sequence of values based on a predicate.

Resizers

• skip(amount): Bypasses a specified number of elements in a sequence.
• take(amount): Returns a specified number of contiguous elements from the start of a sequence.

Sorters

• reverse(): Inverts the order of the elements in a sequence.
• sort(cb): Sorts the elements using a custom comparer function.
• sortByAsc(key): Sorts objects in ascending order based on a property key.
• sortByDesc(key): Sorts objects in descending order based on a property key.
• sortAsc(): Sorts an array of strings or numbers in ascending order.
• sortDesc(): Sorts an array of strings or numbers in descending order.

Pickers (Terminal Methods)

These methods execute the query and return a value.

• all(): Returns all elements of the sequence as an array.
• count(): Returns the number of elements in the sequence.
• sum(cb?): Computes the sum of a sequence of numeric values.
• first(cb?): Returns the first element of a sequence, or the first element that satisfies a condition.
• last(cb?): Returns the last element of a sequence, or the last element that satisfies a condition.

Development

To work on this project, clone the repository and install the dependencies.

npm install

Running Tests

You can run the unit tests using Vitest:

npm run test

To generate a coverage report, run:

npm run coverage

The report will be available in the coverage directory.

License

This project is licensed under the ISC License. See the package.json file for details.