JavaScript Array IndexOf() Method - W3Schools

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JavaScript Array indexOf() ❮ Previous JavaScript Array Reference Next ❯

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:

MethodFinds
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 numberThe 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 »

Array Tutorials:

Array Tutorial

Array Const

Basic Array Methods

Array Search Methods

Array Sort Methods

Array Iteration Methods

Browser Support

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

JavaScript 2009 is supported in all browsers since July 2013:

Chrome23 IE/Edge11 Firefox21 Safari6 Opera15
Sep 2012 Sep 2012 Apr 2013 Jul 2012 Jul 2013
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