PI digits generator in NodeJS

pi.js

const process = require('process');
const fs = require('fs');

let digits = process.argv[2] ?? 9999
let i = 1n;
x = 3n * (10n ** (BigInt(digits) + 20n));
let pi = x;
let pistr16;
let started = new Date();
let digitsCounted;
let seconds;

while (x > 0) {
    x = x * i / ((i + 1n) * 4n);
    pi += x / (i + 2n);
    i += 2n;
    pistr16 = pi.toString(16);

    
    digitsCounted = Math.round(((pistr16.length - x.toString(16).length) * 1.20412) - 20);
    seconds = (((Date.now() - started.getTime())/1000));

    console.log('Calculated ' + digitsCounted.toString() + ' digits out of ' + digits + ' in ' + Math.floor(seconds).toString()+ ' seconds. Hashrate: ' + (digitsCounted/seconds).toString() + ' D/S');
    process.stdout.clearLine(1);
    process.stdout.moveCursor(0, -1);
};

let pee = (pi / (10n ** 20n));

//console.log('3.'+pee.toString().slice(1));

process.stdout.clearLine(1);
process.stdout.moveCursor(0, -1);

console.log('\nCalculated ' + digitsCounted.toString() +' digits of PI in ' + seconds.toString()+ ' seconds. Hashrate: ' + (digitsCounted/seconds).toString() + ' D/S');

fs.writeFileSync('./pi.txt', '3.'+pee.toString().slice(1), 'utf-8');
console.log('\nPI was written to "./pi.txt" file.');