[ Solved ] Why this code is not working?

Question

I learned that JavaScript counts positions from 0. But the following code is not working. Why?

<script>
var str = "Apple, Banana, Kiwi";
var res = str.substr(-0);
document.getElementById("demo").innerHTML = res;
</script>

Answer 1

Not enough info..
Add full code..

It assigns full string...
0 or -0 is same

Answer 2

If the length is 0 or negative value then it returns an empty string.

https://code.sololearn.com/WrvCsd9WY3Ss/#html