Confusion in eloquent javascript power recursion sample

Question

this recursion code is from the book of eloquent javascript

function power(base, exponent) {
  if (exponent == 0) {
    return 1;
  }
  else {
    return base *          


        

Answer 1

But how did base got multiplied by exponent

It doesn't multiply by the exponent.

The exponent is being used as a counter to end the recursive cycle once it's been reduced to 0. The base is instead being multiplied by itself an exponent number of times.

This is supported by each call to power() returning either 1 or the value of base. In the latter case, power() is called again to get 1 or another copy of base to multiply by. And, this repeats until it does finally return 1 as the final multiplier.

            power(2, 3) ==
        2 * power(2, 2) == // base * ...
    2 * 2 * power(2, 1) == // base * (base * ...)
2 * 2 * 2 * power(2, 0) == // base * (base * (base * ...))
2 * 2 * 2 * 1              // base * (base * (base * (1)))

---

The same steps could also be defined with a loop, though using 1 as the initial value rather then at the end:

function power(base, exponent) {
    var result = 1;

    while (exponent) {
        result *= base;
        exponent--;
    }

    return result;
}

console.log(power(2, 3)); // 1 * base * base * base == 1 * 2 * 2 * 2 == 8