Getting return undefined on recursive function javascript

Question

I heard recursive function is powerful so instead going through loop i tried to create a function which increments a number until it reach certain points. when it reaches i tried to return the value, but it give undefined.

CODE

var i=1;
function rec(){
    i++;
    console.log(i);
    if(i > 100){
        return i;
    }else{
        rec();
    }
}

console.log(rec());

Here the i is incrementing until 100. but it returns undefined after the limit. Why is this happening? Also please let me know, it this kind of recursion is good then for loop?

Answer 1

The comment by vaultah is correct:

let i = 1;
function rec() {
    i++;
    console.log(i);
    if (i > 100) {
        return i;
    } else {
        return rec();
    }
}

console.log(rec());

---

Let's take an example that only counts to > 5 and add some output so you can see what happens more easily (but again, stepping through the code with a debugger is the right way to see how this works):

let nesting = 0;
let i = 1;
function rec() {
    let rv;
    ++i;
    ++nesting;
    if (i > 5) {
        log(`${i} > 5, returning ${i}`);
        rv = i;
    } else {
        log(`${i} is not > 5, calling rec`);
        rv = rec();
        log(`Got ${rv} back from rec, returning it`);
    }
    --nesting;
    return rv;
}

log("Final result: " + rec());

function log(msg) {
    console.log(" ".repeat(nesting) + msg);
}

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