:title
dv_group_by

:sig
DValue dv_group_by(DValue tree, function<String (DValue, String)> f)

:see
StringList
0_DValue
filter

:content
Groups children into list-like buckets by the string returned from f.

These helpers are intentionally small data-shaping conveniences for render code, routers, and configuration trees. They are useful when porting habits from React/Next/Remix code where lists of routes, navigation items, cards, or records are transformed close to the rendering boundary.

```cpp
DValue by_section = dv_group_by(menu, [](DValue item, String key) { return(item["section"].to_string()); });
```

Prefer these helpers over open-coded loops when the transformation itself is the important part of the code. Use an explicit loop when mutation, error handling, or side effects are the main concern.

## Related Concepts

- JavaScript / React: `Array.map`, `Array.filter`, `Array.find`, object `pick`/`omit`, and grouping route or navigation records before rendering.
- PHP: `array_map`, `array_filter`, `array_unique`, and associative array projection.
