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JavaScript Array length

The length property sets or returns the number of elements in an array.

How do you find the length of an array in JavaScript?

The JavaScript array length property states the number of items in an array.

To find the length of an array, reference the object array_name. length.

The length property returns an integer.

In this tutorial, you’ll learn about the JavaScript Array length property and how to handle it correctly.

Syntax

Return the length of an array:

array.length

Set the length of an array:

array.length = number

Return Value

The number of elements in the array. It returns the integer just greater than the highest index in an Array.

Below are the examples of the Array length property.

Example – Get Length

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let length = fruits.length;

let city = ["California", "Barcelona", "Paris", "Kathmandu"];

// find the length of the city array
let len = city.length;
console.log(len);

// Output: 4

var companyList = ["Apple", "Google", "Facebook", "Amazon"];
console.log(companyList.length); // Output: 4

var randomList = ["JavaScript", 44];
console.log(randomList.length); // Output: 2

var emptyArray = [];
console.log(emptyArray.length); // Output: 0

Example – Set Length

You can also reassign the length property of an Array using the assignment operator =.

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.length = 2;

This can be used to truncate or extend a given array.

Using Array length in for loop

var languages = ["JavaScript", "Python", "C++", "Java", "Lua"];

// languages.length can be used to find out 
// the number of times to loop over an array
for (i = 0; i < languages.length; i++){
    console.log(languages[i]);
}

Changing length property of Array

var languages = ["JavaScript", "Python", "C++", "Java", "Lua"];

// truncate the Array to 3 elements
languages.length = 3

// Output: [ 'JavaScript', 'Python', 'C++' ]
console.log(languages)

// extend the Array to length 6
languages.length = 6

// Output: [ 'JavaScript', 'Python', 'C++', <3 empty items> ]
console.log(languages)

If the assigned value is more than the original Array length, empty items are appended to the end of the Array.