How does using a return clause before a recursive function call differ from not using one?

Question

I was just experimenting with some recursion and noticed something that confused me. Let me illustrate with some code examples:

function loop(x) {
  if (x >=          


        

Answer 1

The order in which this recursive call will evaluate will be from the last call down. The function that gets evaluated first is the loop(10) which returns a value of 10. The next will be loop(9) and so on. Think about what loop(9) will look like when it is called:

loop(9) {
    if (x >= 10) 
        return x;
    10
}

loop(9) will return undefined. loop(8) will as well... and so on.

Conversely, if you return the value of the recursive call it would look like this:

loop(9) {
    if (x >= 10) 
        return x;
    return 10
}

and by the time your initial function call gets executed it will look like this:

loop(0) {
    if (x >= 10) 
        return x;
    return 10
}

I created a jsfiddle to demonstrated the point: http://jsfiddle.net/TSnxp/