Suggestion: Retain empty arrays in `flattenObject`

[islami00]

When trying to flatten an object with an empty array, the key is omitted entirely if the array is empty. Since empty objects are retained, it would be great if arrays have the same behaviour.

const test = { prop: [], objectProp: {} };

flattenObject(test);
//  current result: { objectProp: {} }
//  expected result: { prop: [], objectProp: {} }

[Yeom-JinHo]

@raon0211 @dayongkr
Hi there 👋

In the flattenObject docs it says: “Empty objects and empty arrays don't appear as keys.”

However, the current implementation behaves differently:

• Empty plain objects ({}) are retained as a leaf value (the key remains).
• Empty arrays ([]) are omitted entirely (the key disappears), since the function always recurses into arrays and an empty array produces no flattened entries.

So at the moment, docs and implementation seem inconsistent.

Which direction would you prefer?

1. Keep the current behavior of preserving {} and update the docs accordingly (and potentially also preserve empty arrays for consistency), or
2. Follow the docs strictly and change the code to omit empty objects as well (so both {} and [] are removed)?

I’d love to align this with the intended behavior before opening a PR. Thanks!

[jidohyun]

Here's a PR related to that issue!
#1571