Very simple JS pi generator

mypi.cpp

// g++ -o mypi -std=c++14 mypi.cpp
#include <iostream>
#include <string>
#include <ctime>
#include <limits>

double myPi(long long loopCount);

typedef std::numeric_limits< double > dbl;

int main(int argc, char *argv[])
{
  using namespace std;

  long long loopCount = 602;
  if (argc >= 2) loopCount = strtoll(argv[1], NULL, 10);

  cout << "loopCount: " + to_string(loopCount) << endl;

  clock_t begin = clock();
  double pi = myPi(loopCount);
  clock_t end = clock();
  double elapsed_secs = double(end - begin) / CLOCKS_PER_SEC;

  cout.precision(dbl::max_digits10);
  cout << "Pi: " << fixed << pi << endl;
  cout << "Time(s): " + to_string(elapsed_secs) << endl;
}

double myPi(long long loopCount){
  double pi = 1.0;
  bool flag = false;
  //600 gives about 2 decimal accuracy, increase for more
  for (long long i = 3; i < loopCount; i+=2){
    if (flag) {
      pi += (1.0/i);
      flag = false;
    }
    else {
      pi -= (1.0/i);
      flag = true;
    }
  }
  return (pi * 4);
}

pi.js

let pi = 1, flag = false;
//600 gives about 2 decimal accuracy, increase for more
for (let i = 3; i < 600; i+=2){
    if (flag) {
      pi += (1/i);
      flag = false;
    }
    else {
      pi -= (1/i);
      flag = true;
    }
}
console.log(pi * 4);

pi.wasm.js

let myPi;
fetch('https://rawgit.com/mattcodez/junk/master/pi.wasm')
.then((res,err) => {
  if (res.type === 'opaque' || res.ok)
    return res.arrayBuffer();
  else {
     console.log('res', res);
     throw new Error(`Unable to fetch WASM.`);
  }
 
})
  .then(bytes => {//console.log('bytes', bytes);
  return WebAssembly.compile(bytes);
})
  .then(module => {
  return WebAssembly.instantiate(module);
})
  .then(instance => {
  myPi = instance.exports._Z4myPiv;
  //console.log(instance.exports)
  let start = Date.now();
  console.log('pi', 4 * myPi());
  let total = Date.now() - start;
  console.log(`ran in ${total} seconds`);
})
.catch(e => console.log(e)); 

pi_worker.js

//same as pi.js but with web workers so that we don't lock the browser
//on long processes
let blob = new Blob([`
let pi = 1, flag = false;
for (let i = 3; i < 600000000; i+=2){
    if (flag) {
      pi += (1/i);
      flag = false;
    }
    else {
      pi -= (1/i);
      flag = true;
    }
}
postMessage(pi * 4);
  
`], { type: "text/javascript" });

let worker = new Worker(window.URL.createObjectURL(blob));
let start = Date.now();
worker.onmessage = function (e){
  let time = Date.now() - start;
  console.log(`pi in ${time} seconds:`, e.data)
}