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JS Functions

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JavaScript Objects HTML DOM Objects


JavaScript Array Search


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;
Try it Yourself »

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
Try it Yourself »

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

includes() is not supported in Internet Explorer.



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 (JavaScript 2015).

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

find() is not supported in Internet Explorer.


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 (JavaScript 2015).

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

findIndex() is not supported in Internet Explorer.


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);
Try it Yourself »

Browser Support

findLast() is an ES2023 feature.

It 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.

It 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 Array Reference

For a complete Array reference, go to our:

Complete JavaScript Array Reference.

The reference contains descriptions and examples of all Array properties and methods.

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