In JavaScript—and many other programming languages—arrays are zero-indexed. This means their indices start counting from 0 instead of 1. Imagine an array of 50 items, for example. Its indices would range from 0 to 49.

If we know there are 50 items in the array, we can easily access the last item using its index, which would be 49 in this case:

var lastFruit = fruits[49];

But what if we don't know how many items there are?

Here's the trick:

The maximum index is always one less than the array's length property.

This means that, for an array of unknown length, you can get the last item by subtracting 1 from its length property:

var lastFruit = fruits[fruits.length - 1];

I would probably use this method even if I did know how many items were in the array, because it's clearer that I intend to get the last item.

I hope this helps!