quick-is-prime

quick-is-prime

Test if a number is prime in constant time, using a cached Sieve of Eratosthenes. This is especially helpful to test many numbers' primality.

Install

$ npm install quick-is-prime

var isPrime = require('quick-is-prime');

Usage

// Simple examples
console.log(isPrime(47)); // true
console.log(isPrime(48)); // false
console.log(isPrime(61)); // true
console.log(isPrime(100)); // false

// More challenging examples
console.log(isPrime(9998903)) // true, takes 1.5 seconds
console.log(isPrime(9893899)) // true, takes less than a millisecond

This module uses a cached Sieve of Eratosthenes for constant time lookup. A new one will be automatically generated if the number you're testing is larger than the currently cached sieve's upper bound.

For best results, check primes highest to lowest. Or alternatively, if you know what the upper bound will be, just check that first to not be concerned with the order.

Tests

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test