JS Practice — Built-in Objects

Array.prototype.findIndex() — find object index by id

📖 Usage Example

const users = [{id:1}, {id:2}, {id:3}]
users.findIndex(u => u.id === 2)  // → 1

Use findIndex() on an object array to find the position of a specific record.

Array.prototype.findIndex() — object arrays

findIndex() is often used with object arrays to get the index of an object with a specific property value.

Challenge: Implement indexOfId(items, id) that returns the index of the item with matching id.

indexOfId([{id:1},{id:2},{id:3}], 2) // → 1
indexOfId([{id:1},{id:2}], 99)       // → -1

💡 Hints (2)

• `findIndex` lets you search by any property, unlike `indexOf` which uses reference equality.
• The returned index can be used to splice, update, or access the element.