A little Sieve of Eratosthenes

sieve.js

const sieve = ( size ) => {

  //TODO: add windowing for the buffer, allocating a fixed-size buffer that gets repopulated when needed

  const buffer = new Uint8Array ( Math.ceil ( size / 8 ) ).fill ( 255 );
  const primes = [];

  let prev = 2;

  for ( let i = 2; i <= size; i++ ) {

    const index = Math.floor ( i / 8 );
    const offset = i % 8;

    if ( buffer[index] & ( 1 << offset ) ) { // is prime

      // const delta = i - prev;
      // primes.push ( delta );
      // prev = i;
      primes.push ( i );

      for ( let j = i + i; j <= size; j += i ) {

        const index = Math.floor ( j / 8 );
        const offset = j % 8;

        buffer[index] &=~ ( 1 << offset );

      }

    }

  }

  console.log ( primes.join ( '\n' ) );

};

sieve ( 1_000_000 );