How does this work?

[Sekvent]

How does this work?

Hello, I have a little logic problem in my head. I was trying to understand how does this code work:

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

power(2,2);

It is from a lesson. What I am trying to find out is that: we ave defined a function with parameters base and exponent. Now it returns 0 if exponent is 1. In other cases it returns base * base^(exponent-1) which is basically x*x to the power of exponent -1.

Now how does base*power(base,exponent-1) work because I have not defined any way in this code to calculate it. As in how does the code know that I am trying to multiply x*x*x...etc.

I do not know if this makes any sense to any of you but if someone could explain.

[rtrethewey]

It's a recursive function. It repeatedly calls itself, decrementing the value of 'exponent' by 1 with each call until exponent equals 0.

When you call power(2,2):
First time through:
return 2 * (power(2,1))
Second time through:
power(2,1)
return 2 * (power(2,0));
Third time through:
power(2,0)
return 1;
Which is returned to the call in the second time through to resolve to:
return 2 * (1);
Which is returned to the call in the first time through to resolve to:
return 2 * 2;
Which equals 4 - and returned as the correct answer.