This is an implementation of the sieve of Eratosthenes. It finds prime numbers for you.
npm install sieve
var sieve = require('sieve'); // primes from 2 to 1000000 var primes = sieve(1000000); // primes from 100 to 1000000 var primes = sieve(1000000, 100);
The sieve returns a Uint32Array, unless you are using a terrible browser, in which case you just get an ordinary array.
On my macbook pro, it found all primes from 2 to 100,000,000 in 2723ms.
It has memory issues with arrays much larger than that. If that is a problem, submit a pull request.