JavaScript Array Search
Array Search Methods
|
Array indexOf() Array lastIndexOf() Array includes() |
Array find() Array findIndex() Array findLast() Array findLastIndex() |
JavaScript Array indexOf()
The indexOf() method searches an array for an element value and returns its position.
Note: The first item has position 0, the second item has position 1, and so on.
Example
Search an array for the item "Apple":
const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.indexOf("Apple") + 1;
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Syntax
array.indexOf(item, start)
| item | Required. The item to search for. |
| start | Optional. Where to start the search. Negative values will start at the given position counting from the end, and search to the end. |
Array.indexOf() returns -1 if the item is not found.
If the item is present more than once, it returns the position of the first occurrence.
JavaScript Array lastIndexOf()
Array.lastIndexOf() is the same as Array.indexOf(), but
returns the position of the last occurrence of the specified element.
Example
Search an array for the item "Apple":
const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.lastIndexOf("Apple") + 1;
Try it Yourself »
Syntax
array.lastIndexOf(item, start)
| item | Required. The item to search for |
| start | Optional. Where to start the search. Negative values will start at the given position counting from the end, and search to the beginning |
JavaScript Array includes()
ECMAScript 2016 introduced Array.includes() to arrays.
This allows us to check if an element is present in an array (including NaN, unlike indexOf).
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.includes("Mango"); // is true
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Syntax
array.includes(search-item)
Array.includes() allows to check for NaN values. Unlike Array.indexOf().
Browser Support
includes() is an ECMAScript 2016 feature.
ES 2016 is fully supported in all modern browsers since March 2017:
| Chrome 52 |
Edge 15 |
Firefox 52 |
Safari 10.1 |
Opera 39 |
| Jul 2016 | Apr 2017 | Mar 2017 | May 2017 | Aug 2016 |
JavaScript Array find()
The find() method returns the value of the first array element that passes a
test function.
This example finds (returns the value of) the first element that is larger than 18:
Example
const numbers = [4, 9, 16, 25, 29];
let first =
numbers.find(myFunction);
function myFunction(value, index, array) {
return
value > 18;
}
Try it Yourself »
Note that the function takes 3 arguments:
- The item value
- The item index
- The array itself
Browser Support
find() is an ES6 feature.
ES6 is fully supported in all modern browsers since June 2017:
| Chrome 51 |
Edge 15 |
Firefox 54 |
Safari 10 |
Opera 38 |
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |
JavaScript Array findIndex()
The findIndex() method returns the index of the first array element that
passes a test function.
This example finds the index of the first element that is larger than 18:
Example
const numbers = [4, 9, 16, 25, 29];
let first =
numbers.findIndex(myFunction);
function myFunction(value, index, array) {
return
value > 18;
}
Try it Yourself »
Note that the function takes 3 arguments:
- The item value
- The item index
- The array itself
Browser Support
findIndex() is an ES6 feature.
ES6 is fully supported in all modern browsers since June 2017:
| Chrome 51 |
Edge 15 |
Firefox 54 |
Safari 10 |
Opera 38 |
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |
JavaScript Array findLast() Method
ES2023 added the findLast() method that will start from the end of an array and return the value of the first element that satisfies a condition.
Example
const temp = [27, 28, 30, 40, 42, 35, 30];
let high = temp.findLast(x => x > 40);
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Browser Support
findLast() is an ES2023 feature.
JavaScript 2023 is supported in all modern browsers since July 2023:
| Chrome 110 |
Edge 110 |
Firefox 115 |
Safari 16.4 |
Opera 96 |
| Feb 2023 | Feb 2023 | Jul 2023 | Mar 2023 | May 2023 |
JavaScript Array findLastIndex() Method
The findLastIndex() method finds the index of the last element that satisfies a condition.
Example
const temp = [27, 28, 30, 40, 42, 35, 30];
let pos = temp.findLastIndex(x => x > 40);
Try it Yourself »
Browser Support
findLastIndex() is an ES2023 feature.
JavaScript 2023 is supported in all modern browsers since July 2023:
| Chrome 110 |
Edge 110 |
Firefox 115 |
Safari 16.4 |
Opera 96 |
| Feb 2023 | Feb 2023 | Jul 2023 | Mar 2023 | May 2023 |
Complete JavaScript Reference
For a complete reference to all JavaScript properties and methods, with full descriptions and many examples, go to:
W3Schools' Full JavaScript Reference.
The reference inludes all JavaScript updates from 1999 to 2025.
