indexOf

The indexOf() method returns the index of the first occurrence of an element in an array.

Interactive example

Syntax

Classic signature

function indexOf<
	GenericElement extends unknown
>(
	input: readonly GenericElement[], 
	element: GenericElement, 
	fromIndex?: number
): number | undefined

Curried signature

function indexOf<
	GenericElement extends unknown
>(
	element: GenericElement
): (input: readonly GenericElement[]) => number | undefined

Parameters

• input: The array to search in.
• element: The element to search for.
• fromIndex: Starting index for the search (optional).

Return value

The index of the first occurrence of the element, or undefined if the element is not found.

See also

• lastIndexOf - Returns the index of the last occurrence
• findIndex - Finds the index with a condition

Sources

• MDN Web Docs - Array.indexOf()