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.

Syntax

typedarray.lastIndexOf(searchElement[, fromIndex = typedarray.length])

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

var 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 Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'TypedArray.prototype.lastIndexOf' in that specification.
Standard Initial definition.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'TypedArray.prototype.lastIndexOf' in that specification.
Draft  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) 37 (37) No support (Yes) 10
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 37 (37) No support No support 10

Compatibility notes

  • Starting with Firefox 47 (Firefox 47 / Thunderbird 47 / SeaMonkey 2.44),  this method will no longer return -0.
    For example, new Uint8Array([0]).lastIndexOf(0, -0) will now always return +0 (bug 1242043).

See also

Document Tags and Contributors

 Contributors to this page: David_Gilbertson, eduardoboucas, fscholz
 Last updated by: David_Gilbertson,