`Array.prototype.lastIndexOf()`

Returns the last index at which a given element is found, searching backwards.

Syntax

arr.lastIndexOf(searchElement, fromIndex)

Name	Type	Required	Description
`searchElement`	`any`	Yes	The value to locate, compared using strict equality (===).
`fromIndex`	`number`	No	Index to start searching backwards from. Negative values count from the end. Defaults to the last index.

number — The last matching index, or -1 if not found.

console.log(['a', 'b', 'c', 'b'].lastIndexOf('b'));

Output

console.log([1, 2, 3].lastIndexOf(9));

Output

-1

Searches the array in reverse but returns the absolute (forward) index. Uses strict equality and cannot find NaN.