JavaScript Array Search

Array Search Methods

Complete JavaScript Array Reference ## JavaScript Array indexOf() The indexOf() method searches an array for an element value and returns its position.

Example

const fruits = ["Apple", "Orange", "Apple", "Mango"];

let position = fruits.indexOf("Apple") + 1;

Syntax

array.indexOf(item, start)

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

const fruits = ["Apple", "Orange", "Apple", "Mango"];

let position = fruits.lastIndexOf("Apple") + 1;

Syntax

array.lastIndexOf(item, start)

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

Syntax

array.includes(search-item)

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;
}

Note that the function takes 3 arguments:

• The item value
• The item index
• The array itself

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;
}

Note that the function takes 3 arguments:

• The item value
• The item index
• The array itself

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);

Browser Support

findLast() is an ECMAScript 2023 feature.

JavaScript 2023 is supported in all modern browsers since July 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);

Browser Support

findLastIndex() is an ECMAScript 2023 feature.

JavaScript 2023 is supported in all modern browsers since July 2023: