JavaScript Arrays Searching

Searching is one of the most common operations performed on arrays. JavaScript provides several built-in methods that help you find elements, check if an element exists, or get the position of an element.

Instead of writing long loops, you can use these methods to search arrays quickly and easily.

indexOf()

The indexOf() method returns the index of the first matching element.

If the value is not found, it returns -1.

Syntax

arrayName.indexOf(value)

Example

let fruits = ["Apple", "Banana", "Mango", "Orange"];
console.log(fruits.indexOf("Mango"));

Output

2

Value Not Found

let fruits = ["Apple", "Banana", "Mango"];
console.log(fruits.indexOf("Grapes"));

Output

-1

lastIndexOf()

The lastIndexOf() method returns the index of the last occurrence of a value.

Syntax

arrayName.lastIndexOf(value)

Example

let numbers = [10, 20, 30, 20, 40];
console.log(numbers.lastIndexOf(20));

Output

3

includes()

The includes() method checks whether an element exists in an array.

It returns either true or false.

Syntax

arrayName.includes(value)

Example

let fruits = ["Apple", "Banana", "Mango"];
console.log(fruits.includes("Banana"));

Output

true

Element Does Not Exist

let fruits = ["Apple", "Banana", "Mango"];
console.log(fruits.includes("Orange"));

Output

false

find()

The find() method returns the first element that satisfies a condition.

If no element matches, it returns undefined.

Syntax

arrayName.find(function(element) {
    return condition;
});

Example

let numbers = [5, 12, 18, 25];
let result = numbers.find(function(num) {
    return num > 10;
});
console.log(result);

Output

12

findIndex()

The findIndex() method returns the index of the first element that matches a condition.

If no element matches, it returns -1.

Syntax

arrayName.findIndex(function(element) {
    return condition;
});

Example

let numbers = [5, 12, 18, 25];
let result = numbers.findIndex(function(num) {
    return num > 10;
});
console.log(result);

Output

1

Important Points

• indexOf() returns the first matching index.
• lastIndexOf() returns the last matching index.
• includes() returns true or false.
• find() returns the first matching element.
• findIndex() returns the index of the first matching element.
• If nothing is found, indexOf() and findIndex() return -1, while find() returns undefined.

Comparison

Example

let students = ["Rahul", "Aman", "Priya", "Neha"];
console.log(students.includes("Priya"));
console.log(students.indexOf("Neha"));
console.log(students.indexOf("Rohit"));

Output

true
3
-1