JS Practice — Built-in Objects

Array.prototype.fill() — fill last elements with negative index

📖 Usage Example

const arr = [1, 2, 3, 4, 5]
arr.fill(0, -3)  // → [1, 2, 0, 0, 0]
// fills the last 3 elements

Use a negative start index with fill() to fill elements counting from the end.

Array.prototype.fill() — negative start index

fill() supports negative indices for start and end. fill(val, -2) fills the last two elements of the array.

Challenge: Implement fillLastTwo(arr, val) that fills the last 2 elements of arr with val using arr.fill(val, -2).

fillLastTwo([1, 2, 3, 4, 5], 0) // → [1, 2, 3, 0, 0]
fillLastTwo([10, 20], 99)       // → [99, 99]

💡 Hints (2)