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TypedArray.prototype.lastIndexOf()

The lastIndexOf() method 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(). TypedArray is one of the typed array types here.

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Syntax

lastIndexOf(searchElement)
lastIndexOf(searchElement, fromIndex)

Parameters

searchElement: Element to locate in the typed array.
fromIndex: Optional. The index at which to start searching backwards. Defaults to the typed array's length, i.e. the whole typed array will be searched. If the index is greater than or equal to the length of the typed array, the whole typed array will be searched. If negative, it is taken as the offset from the end of the typed array. Note that even when the index is negative, the typed array is still searched from back to front. If the calculated index is less than 0, -1 is returned, i.e. the typed array will not be searched.

Return value

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

Description

lastIndexOf compares searchElement to elements of the typed array using strict equality (the same method used by the ===, or triple-equals, operator).

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

Specification
ECMAScript Language Specification # sec-%typedarray%.prototype.lastindexof

Browser compatibility

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	Deno	Node.js
`lastIndexOf`	45	12	37 Starting with Firefox 47, this method will no longer return `-0`. For example, `new Uint8Array([0]).lastIndexOf(0, -0)` will now always return `+0`.	No	32	10	45	45	37 Starting with Firefox 47, this method will no longer return `-0`. For example, `new Uint8Array([0]).lastIndexOf(0, -0)` will now always return `+0`.	32	10	5.0	1.0	4.0.0