tiny-async-trampoline.js

//@flow

function TCROA(iterate) {
  return function(initialValue, resolve) {
    function next(value) {
      setImmediate(() => iterate(value, resolve, next), 0);
    }
    
    next(initialValue);
  }
}

const factorial = do {
  const factorial_ = TCROA(({ n, acc }, resolve, next) => {
    if (n === 0) {
      return resolve(acc);
    } else {
      return next({ n: n - 1, acc: n + acc });
    }
  });

  n => factorial_({ n, acc: 1 }, result => console.log(result)); 
};

factorial(100000);