Anyone mind explaining this js problem?

Question

function fib(num){
if(num<=2)
return 1;
return fib(num-1)+fib(num-2);
}
document.write(fib(6));

I just can't wrap my head around this one. I don't see how were getting an answer of 8. What do I need to know to be able to understand it?

Answer 1

function fib(num){
if(num<=2)
return 1;
return fib(num-1)+fib(num-2);
}
document.write(fib(6));

=> The function is called with num = 6 and it returns fib(5) + fib(4)

fib(5) returns fib(4) + fib(3)
fib(4) returns fib(3) + fib(2)
fib(3) returns 1 + 1 = 2
fib(2) returns 1
........

fib(4) = 2+1= 3
fib(5) = 3+2 = 5

Similarly,
fib(6) = fib(5) + fib(4) = 5 + 3 = 8

Answer 2

thanks very much for a great explanation