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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.


Definition and Usage

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.

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 right to left).

See Also:

The lastIndexOf() method


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, ...


Browser Support

indexOf() is an ES5 feature (JavaScript 2009). It is fully supported in all modern browsers:

Chrome IE Edge Firefox Safari Opera
Yes 9.0 Yes Yes Yes Yes

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 »