TypedArray.prototype.lastIndexOf()

The lastIndexOf() method of {{jsxref("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 {{jsxref("Array.prototype.lastIndexOf()")}}.

{{InteractiveExample("JavaScript Demo: TypedArray.prototype.lastIndexOf()")}}

```js interactive-example 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

```js-nolint
lastIndexOf(searchElement)
lastIndexOf(searchElement, fromIndex)

Parameters#

• searchElement
• : Element to locate in the typed array.
• fromIndex {{optional_inline}}
• : 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 {{jsxref("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#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

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