I had the same question! I digged in and were able to find a very interesting behavior of an object numeric property - If we loop over an object that has integer properties, the properties are sorted (ascending). However, if the key are non-integers, then they are listed in the creation order. In this case, the last should be the largest integer that we want to return if there is a tie!

You can read more from this article https://javascript.info/object#ordered-like-an-object