async.js

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

const LOOPS = process.env.LOOPS || 2;

// start mesuring time
const hrstart = process.hrtime()

for (i=1; i <= LOOPS; i++) {
   const index = i;
   const cb = () => {
    const hrend = process.hrtime(hrstart);
    console.info('Execution time crypto %d (hr): %ds %dms', index, hrend[0], hrend[1] / 1000000);

  }
  const key = crypto.scrypt(password, 'salt', 24, cb);
}

const pend = process.hrtime(hrstart);
console.info('Process ended in (hr): %ds %dms', pend[0], pend[1] / 1000000);