JS Built-ins
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ArrayArray.prototype.indexOfintermediate

Array.prototype.indexOf() — search from index

📖 Usage Example
const arr = [1, 2, 3, 1, 2]
arr.indexOf(1)     // → 0
arr.indexOf(1, 1)  // → 3  (starts at index 1)

Pass a fromIndex to indexOf() to skip past the first occurrence and find later ones.

Array.prototype.indexOf() — fromIndex

The optional second argument fromIndex tells indexOf where to start searching. This lets you find subsequent occurrences after a known position.

Challenge: Implement indexOfFrom(arr, val, from) that uses arr.indexOf(val, from).

indexOfFrom([1, 2, 1, 2], 2, 2) // → 3
indexOfFrom([1, 2, 1, 2], 1, 1) // → 2
💡 Hints (2)
  • • `fromIndex` specifies where to start — elements before it are skipped.
  • • To find all occurrences, loop calling `indexOf(val, lastIndex + 1)` until `-1` is returned.