JavaScript Array indexOf() Method

indexOf()The method returns the first index where the given element can be found in the array.

If the element is not found, it will return-1.

If the element exists multiple times, it will return the position of the first occurrence.

If you want to search from the end, please uselastIndexOf()method.

Note:For more information on String methods, seeString.indexOf().

Syntax:

array.indexOf(element, start)

Example

var fruits = ['Banana', 'Mango', 'Apple', 'Orange'];
fruits.indexOf('Apple');

The numbers in the table specify the first browser version that fully supports the indexOf() method:

Method
indexOf()	Yes	Yes	34	Yes	9

Parameter	Description
element	(Required) The element to locate in the array
start	(Optional) The index of the element to start searching from. The default value is 0

Return value:	The index of the first occurrence of the element in the array; if not found, return -1
JavaScript version:	ECMAScript 5

From index2Start searching from:

Example

var fruits = ['Banana', 'Mango', 'Apple', 'Orange'];
fruits.indexOf('Mango',　2);

If the given parameter does not exist in the array, it will return-1:

Example

var fruits = ['Banana', 'Mango', 'Apple', 'Orange'];
fruits.indexOf('Beer');//　Back　-1