# Array `slice` and Indexing

Your snippet uses `slice` and index-based access to create weekly intervals.

## `slice(0, -1)`

```ts
const periodStarts = alignedStarts.slice(0, -1);
```

- Start at index `0`.
- Stop before the last item (`-1` means from the end).
- Useful when each `start` needs a following `end` item.

## Index access

```ts
const end = alignedStarts[index + 1];
```

- Gets the next boundary after the current `start`.

## Python comparison

```py
period_starts = aligned_starts[:-1]
end = aligned_starts[index + 1]
```

This is the same concept as Python slicing and list indexing.