JavaScript Array indexOf()
Examples
Find the first index of "Apple":
let index = fruits.indexOf("Apple");
Start at index 3:
let index = fruits.indexOf("Apple", 3);
More examples below.
Description
TheindexOf() method returns the first index (position) of a specified value.
TheindexOf() method returns -1 if the value is not found.
TheindexOf() 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
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:
let index = fruits.indexOf("Apple", -1);
Array Tutorials:
Browser Support
indexOf() is an ECMAScript5 (ES5 2009) feature.
JavaScript 2009 is supported in all browsers sinceJuly 2013:
| Chrome 23 | IE/Edge 11 | Firefox 21 | Safari 6 | Opera 15 |
| Sep 2012 | Sep 2012 | Apr 2013 | Jul 2012 | Jul 2013 |
