How to Check a Value Exist at Certain Array Index in JavaScript ?

In this article, we will learn how to check if a value exists at a certain array index in JavaScript. Arrays are used to store multiple values in a single variable. Each value in an array has a numeric index, starting from zero. You can access the values in an array using their index.

Below are the different ways to check if a value exists at a specific index in an array:

Using the typeof operator

In JavaScript, the typeof operator returns the data type of its operand in the form of a string. The operand can be any object, function, or variable. If the value is undefined, then it doesn’t exist.

Syntax:

typeof (operand);

Example: In this example, we will see the use of typeof operator for checking the value.

Javascript

let arr = [1, 2, 3, 4, 5];
let value = 3;

if (typeof arr[value] !== "undefined") {
    console.log(`Value ${value} exists
        at index ${value - 1}`);
} else {
    console.log(`Value ${value} doesn't
        exist at index ${value - 1}`);
}

Output

Value 3 exists 
        at index 2

Using the in operator

The in operator checks if a given property or index exists in the object. For an array, you can use the in operator to check if an index exists or not.

Syntax:

prop in object

Example: In this example, we will see the use of in operator.

Javascript

let arr = [1, 2, 3, 4, 5];
let n = 3;

if (n in arr) {
    console.log(`Value ${n} exists
        at index ${arr.indexOf(n)}`);
} else {
    console.log(`Value ${n} does not
        exist in the array`);
}

Output

Value 3 exists 
        at index 2

Using the hasOwnProperty() method

The hasOwnProperty() method is used to check if an object has a specific property or index. In the case of an array, you can use this method to check if an index exists.

Syntax:

object.hasOwnProperty( prop )

Example: In this example, we will see the use hasOwnProperty() method.

Javascript

const arr = ['Geeksforgeeks', 'GFG', 'gfg'];

if (arr.hasOwnProperty(1)) {
    console.log(arr[1]);
    console.log('The index exists in the array')
} else {
    console.log('The specified index does NOT exist');
}

Output

GFG
The index exists in the array

Using lodash _.includes() method

Lodash _.includes() method is used to find whether the value is in the collection or not. If the collection is a string, it will be tested for a value sub-string, otherwise SameValueZero() method is used for equality comparisons. If the index is given and is negative, the value is tested from the end indexes of the collection as the offset.

Syntax:

_.includes( collection, value, index );

Example 1: In this example, we are checking whether the given value is present in the given collection or not by the use of the _.includes() method.

Javascript

// Requiring the lodash library
const _ = require("lodash");

// Collection of string
let name = ['gfg', 'geeks',
    'computer', 'science', 'portal'];

// Check value is found
// or not by _.includes() method
console.log(_.includes(name, 'computer'));

// Check value is found or
// not by _.includes() method
console.log(_.includes(name, 'geeeks'));

// Check value is found or
// not by _.includes() method
console.log(_.includes(name, 'gfg', 2));

Output:

true
false
false