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JavaScript Array indexOf() Method

JavaScript Array indexOf() Examples

Find the first index of "Apple":

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let index = fruits.indexOf("Apple");

Try it Yourself »

Start at index 3:

const fruits = ["Banana", "Orange", "Apple", "Mango", "Apple"];
let index = fruits.indexOf("Apple", 3);

Try it Yourself »

More examples below.

Description

The indexOf() method returns the first index (position) of a specified value.

The indexOf() method returns -1 if the value is not found.

The indexOf() method starts at a specified index and searches from left to right (from the given start postion to the end of the array).

By default the search starts at the first element and ends at the last.

Negative start values counts from the last element (but still searches from left to right).

Array Find Methods: Method Finds includes() Returns true if an array contains a specified value indexOf() The index of the first element with a specified value lastIndexOf() The index of the last element with a specified value find() The value of the first element that passes a test findIndex() The index of the first element that passes a test findLast() The value of the last element that passes a test findLastIndex() The index of the last element that passes a test Syntax

array.indexOf(item, start)

Parameters Parameter Description item Required.
The value to search for. start Optional.
Where to start the search.
Default value is 0.
Negative values start the search from the end of the array. Return Value Type Description A number The index (position) of the first item found.
-1 if the item is not found. Note

In an array, the first element has index (position) 0, the second has index 1, ...

More Examples

Find the first index of "Apple", starting from the last element:

const fruits = ["Banana", "Orange", "Apple", "Mango", "Apple"];
let index = fruits.indexOf("Apple", -1);

Try it Yourself » Browser Support

indexOf() is an ECMAScript5 (ES5 2009) feature.

JavaScript 2009 is supported in all browsers since July 2013:

Chrome
23 IE/Edge
11 Firefox
21 Safari
6 Opera
15 Sep 2012 Sep 2012 Apr 2013 Jul 2012 Jul 2013

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