JS Built-ins
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ArrayArray.prototype.fillbeginner

Array.prototype.fill() — fill entire array

📖 Usage Example
const arr = [1, 2, 3, 4]
arr.fill(0)  // → [0, 0, 0, 0]

Use fill() without indices to replace every element with a single value.

Array.prototype.fill()

Array.prototype.fill(value, start?, end?) fills all elements from start to end (exclusive) with a static value. Without start/end, it fills the entire array. The method mutates and returns the original array.

Challenge: Implement fillAll(arr, val) that fills the entire array with val using .fill(val).

fillAll([1, 2, 3], 0)   // → [0, 0, 0]
fillAll([1, 2, 3], 'x') // → ['x', 'x', 'x']
💡 Hints (2)
  • • `fill()` mutates the original array and returns it — it does not create a copy.
  • • To avoid mutation, call `fill()` on `[...arr]` or `arr.slice()`.