Recursive power function: Why does this work if there's no initial return value?

Question

because power(base, exponent) has no return value unless exponent is 0, initially, shouldn\'t power(base, exponent -1) return \'undefined\', and therefore be unmultipliable,

Answer 1

function pow(base, exponent) {
    if (exponent === 0) return 1;
    if (exponent > 0) {
        return base * pow(base, exponent - 1)
    } else {
        // handle negative exponent
        return 1 / base * pow(base, exponent + 1)
    }
}