JS Built-ins
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ArrayArray.prototype.keysbeginner

Array.prototype.keys() — count the keys

📖 Usage Example
const arr = ['x', 'y', 'z']
[...arr.keys()].length  // → 3  (same as arr.length)

Spreading keys() into an array lets you count or work with the set of indices.

Array.prototype.keys() — number of keys

The number of keys yielded by arr.keys() is always the same as arr.length. This exercise makes that relationship explicit.

Challenge: Implement countKeys(arr) that returns the number of keys in the array (i.e. how many indices exist).

countKeys([10, 20, 30]) // → 3
countKeys([])           // → 0
💡 Hints (2)
  • • The count of keys always equals `arr.length`.
  • • Convert with `Array.from()` then access `.length`, or just use `arr.length` directly.