There's no need to recalculate the factorials and powers from scratch each time around the loop. Remember the last values and just multiply to get the next value.

Approximate idea (untested, and by a Javascript novice, so likely containing some mistakes):

let PI = 0;
let top = 1;
let pow2 = 2;
let denominator = 1;
for (let i = 1;  i <= 80;  i++) {
  PI += top * top * pow2 / denominator;
  top *= i;
  pow2 *= 2;
  denominator *= (2 * i) * (2 * i + 1);
}