TypedArray.prototype.lastIndexOf()

The lastIndexOf() method of TypedArray instances returns the last index at which a given element can be found in the typed array, or -1 if it is not present. The typed array is searched backwards, starting at fromIndex. This method has the same algorithm as Array.prototype.lastIndexOf().

Try it

const uint8 = new Uint8Array([10, 20, 50, 50, 50, 60]);

console.log(uint8.lastIndexOf(50, 5));
// Expected output: 4

console.log(uint8.lastIndexOf(50, 3));
// Expected output: 3

Syntax

lastIndexOf(searchElement)
lastIndexOf(searchElement, fromIndex)

Parameters

searchElement

Element to locate in the typed array.

fromIndex Optional

Zero-based index at which to start searching backwards, converted to an integer.

Return value

The last index of searchElement in the typed array; -1 if not found.

Description

See Array.prototype.lastIndexOf() for more details. This method is not generic and can only be called on typed array instances.

Examples

Using lastIndexOf()

const uint8 = new Uint8Array([2, 5, 9, 2]);
uint8.lastIndexOf(2); // 3
uint8.lastIndexOf(7); // -1
uint8.lastIndexOf(2, 3); // 3
uint8.lastIndexOf(2, 2); // 0
uint8.lastIndexOf(2, -2); // 0
uint8.lastIndexOf(2, -1); // 3

Specifications

• ECMAScript® 2027 Language Specification

See also

• Polyfill of TypedArray.prototype.lastIndexOf in core-js
• JavaScript typed arrays guide
• TypedArray
• TypedArray.prototype.findIndex()
• TypedArray.prototype.findLastIndex()
• TypedArray.prototype.indexOf()
• Array.prototype.lastIndexOf()
• String.prototype.lastIndexOf()