Function arrayGetOrExtend

arrayGetOrExtend<T>(arr: T[], index: number, default_value: T): T
Gets an element, extending with scalar values or shallow copies if out of bounds.
Type Parameters
- T
  Element type.
Parameters
- arr: T[]
  The dense array.
- index: number
  Integer array index from 0 through 2 ** 32 - 2.
- default_value: T
  Scalar value, plain record, or array template for new entries.
Returns T
The element at index.
Throws
If index is not a valid array index.

Throws
If extension requires copying an unsupported template.

Remarks
Scalars (including null and undefined) are stored unchanged. For objects, copies array elements or enumerable own record properties, retaining nested references. Object templates must have this realm's Object.prototype or Array.prototype, or a null prototype for records. Null-prototype records retain their null prototype. Existing entries are returned without inspecting the template. Use arrayGetOrExtendWith for built-ins, class instances, or templates from another realm.
Example
```
const rows: number[][] = [];
arrayGetOrExtend(rows, 1, [0]); // [0]; rows is [[0], [0]]
rows[0]!.push(1);              // rows[1] remains [0]

const values: bigint[] = [];
arrayGetOrExtend(values, 2, 4n); // 4n; values is [4n, 4n, 4n]
arrayGetOrExtend([], 0, "foo");  // "foo"
arrayGetOrExtend([], 0, null);   // null
```
- Defined in data-structure/array.ts:58