ReferenceError: copy is not defined

## Error

```
copy is not defined
```

## Stack trace

```
<anonymous>:51
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [ReferenceError: copy is not defined](https://thalamus-ai.sentry.io/issues/119043227/)
- **Culprit**: ?(<anonymous>)
- **First seen:** May 11, 2026