JS Practice — Built-in Objects

Replace Element at Index

📖 Usage Example

const arr = [1, 2, 3, 4]
arr.with(1, 99)  // → [1, 99, 3, 4]
arr              // → [1, 2, 3, 4]  (unchanged)

Use with(index, value) to return a new array with one element replaced, leaving the original intact.

Array.prototype.with

The with() method returns a new array with the element at the given index replaced by the provided value.

Implement replaceAt that returns arr.with(index, val).

💡 Hints (2)