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 |
|---|---|
| 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 »
Array Tutorials:
Browser Support
indexOf() is an ECMAScript5 (ES5) feature.
ES5 (JavaScript 2009) is fully supported in all modern 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 |
