Build up a value one iteration at a time.

Loop Accumulators

loop_accumulator.js
const multiplier = 2;
let product = 1;
for (let i = 1; i <= 4; i += 1) {
  product *= multiplier;
}

console.log("multiplier=" + multiplier);
console.log("product=" + product);
loop-accumulator An accumulator starts with an initial value and changes during each loop pass.