NOTE
You can’t use subscript syntax to append a new item to the end of an array. If you try to use subscript
syntax to retrieve or set a value for an index that is outside of an array’s existing bounds, you will trigger a
runtime error. However, you can check that an index is valid before using it, by comparing it to the array’s
count property. Except when count is 0 (meaning the array is empty), the largest valid index in an array will
always be count - 1, because arrays are indexed from zero.