prime-lib

• About
• Installation
• Usage
  • JavaScript
  • TypeScript
  • RXJS
• API

About

Popular prime number functions, implemented in TypeScript, with focus on memory efficiency and performance, to be friendly for Web apps, and RXJS in particular.

It features many well-known optimization methods, such as Sieve of Eratosthenes, Meissel Lehmer, etc.

See the following resources:

• API - all available functions
• WiKi - to help choose a prime generator
• Benchmarks - to see the performance

Installation

$ npm i prime-lib

Usage

Follow the usage examples below, based on your development environment.

JavaScript

Generating an array with the first 10 primes:

const {generatePrimes, stopOnCount} = require('prime-lib');

const i = generatePrimes(); // create infinite primes iterator 
const s = stopOnCount(i, 10); // stop-iterator after 10 values

const values = [...s]; // 2, 3, 5, 7, 11, 13, 17, 19, 23, 29

TypeScript

Generating an array of all primes up to 17:

import {generatePrimes, stopOnValue} from 'prime-lib';

const i = generatePrimes(); // create infinite primes iterator
const s = stopOnValue(i, 17); // stop-iterator when value reaches 17

const values = [...s]; // 2, 3, 5, 7, 11, 13, 17

RXJS

Adding a reusable RXJS wrapper first:

import {Observable, from} from 'rxjs';
import {generatePrimes, IPrimeOptions} from 'prime-lib';

export function primes(options?: IPrimeOptions): Observable<number> {
    return from(generatePrimes(options));
}

• Generating the first 10 primes:

import {take} from 'rxjs';

primes().pipe(take(10))
    .subscribe(prime => {
        // 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
    });

• Generating 10 primes after 100:

import {take} from 'rxjs';

primes({start: 100}).pipe(take(10))
    .subscribe(prime => {
        // 101, 103, 107, 109, 113, 127, 131, 137, 139, 149
    });

• Maximum-performance, buffered primes generation:

primes({boost: 10})
    .subscribe(prime => {
        // 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
    });

• Detecting primes in another sequence:

import {range, filter} from 'rxjs';
import {isPrime} from 'prime-lib';

range(0, 20).pipe(filter(a => isPrime(a)))
    .subscribe(prime => {
        // 2, 3, 5, 7, 11, 13, 17, 19
    });

API

Prime generators:

• generatePrimes() - efficiency-focused, infinite prime generator
• generatePrimes({start: x}) - efficiency-focused, infinite prime generator, starting from x
• generatePrimes({boost: n}) - performance-focused prime generator, for up to n primes

Popular prime functions:

• isPrime(x) - verifies if x is a prime number
• countPrimes(x) - precise primes counter, up to x, using Meissel Lehmer algorithm
• countPrimesApprox(x) - instant primes counter, up to x, with error margin < 1%
• primeFactors(x) - calculates prime factorization

Work-in-progress:

• nthPrime(n) - returns prime from index (not implemented yet)
• nthPrimeApprox(n) - returns approximate prime from index (not implemented yet)

Extra helpers:

• cachePrimes(n) - creates a gap-compressed cache of n primes (see WiKi)
• stopOnCount(iterator, count) - stops the iterator, once count has been reached
• stopOnValue(iterator, maxValue) - stops the iterator when maxValue is exceeded
• stopWhen(iterator, cb) - stops the iterator when the callback returns a truthy value