JavaScript Array Search Methods

Array indexOf()

The indexOf() method searches an array for a specific element and returns its first occurrence index. If the element is not found, it returns -1.

Example

Search for the position of "Apple":

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const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.indexOf("Apple"); // 0‍

Syntax

array.indexOf(item, start)

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• item: Required. The item to search for.
• start: Optional. The position to start the search. Negative values start from the end.

Array lastIndexOf()

The lastIndexOf() method searches an array for a specific element and returns its last occurrence index. If the element is not found, it returns -1.

Example

Search for the last position of "Apple":

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const fruits = ["Apple", "Orange", "Apple", "Mango"];let position = fruits.lastIndexOf("Apple"); // 2

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Syntax

array.lastIndexOf(item, start)

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• item: Required. The item to search for.
• start: Optional. The position to start the search. Negative values start from the end.

Array includes()

The includes() method checks if an array contains a specified element, returning true or false.

Example

Check if "Mango" is in the array:

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const fruits = ["Banana", "Orange", "Apple", "Mango"];let hasMango = fruits.includes("Mango"); // true‍

Syntax

array.includes(item)

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• item: Required. The item to search for.

Array find()

The find() method returns the value of the first element that passes a provided test function.

Example

Find the first number greater than 18:

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const numbers = [4, 9, 16, 25, 29];let first = numbers.find(value => value > 18); // 25

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Array findIndex()

The findIndex() method returns the index of the first element that passes a provided test function.

Example

Find the index of the first number greater than 18:

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const numbers = [4, 9, 16, 25, 29];let index = numbers.findIndex(value => value > 18); // 3

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Array findLast()

The findLast() method returns the value of the last element that satisfies a provided test function, starting from the end of the array.

Example

Find the last temperature greater than 40:

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const temps = [27, 28, 30, 40, 42, 35, 30];let high = temps.findLast(temp => temp > 40); // 42

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Array findLastIndex()

The findLastIndex() method returns the index of the last element that satisfies a provided test function, starting from the end of the array.

Example

Find the index of the last temperature greater than 40:

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const temps = [27, 28, 30, 40, 42, 35, 30];let index = temps.findLastIndex(temp => temp > 40); // 4

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Browser Support

• indexOf(): Supported in all modern browsers.
• lastIndexOf(): Supported in all modern browsers.
• includes(): Supported in modern browsers since March 2017.
• find() and findIndex(): Supported in modern browsers since June 2017.
• findLast() and findLastIndex(): Supported in modern browsers since July 2023.

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