Function defaultIfEmpty

defaultIfEmpty<TElement>(
source: Iterable<TElement>,
value?: TElement | null,
): IEnumerable<TElement | null>
Supplies fallback content when the sequence contains no elements.
Type Parameters
- TElement
  Type of elements within the source iterable.
Parameters
- source: Iterable<TElement>
  The source iterable.
- Optionalvalue: TElement | null
  Optional value returned in a singleton sequence when the source is empty. Defaults to null.
Returns IEnumerable<TElement | null>
The original sequence when it has elements; otherwise, a singleton sequence containing the provided value.
Remarks
Use this to ensure downstream operators always receive at least one element.
Example
```
const empty = [];
const withDefault = defaultIfEmpty(empty, 0).toArray();
console.log(withDefault); // [0]

const numbers = [1, 2, 3];
const withDefault2 = defaultIfEmpty(numbers, 0).toArray();
console.log(withDefault2); // [1, 2, 3]
```
- Defined in src/enumerator/functions/defaultIfEmpty.ts:22