Finding the length of arrays and strings in JavaScript

This tutorial explains how to find the length of an array (how many elements are in an array), the length of an element in an array, and the length of a string (how many characters in a string). This can be quite useful in programming, for example, if you wanted to:

  • find out how many items a player has in the inventory in a game (checking the length of an inventory array)
  • find out how many products are in a user’s shopping cart in an online shopping app (checking the length of a shopping cart array)
  • check that a user’s password is long enough for increased security (checking length of a password stored as a string)

Watch the video below and scroll down to see the sample code:

Here is the sample HTML code:

<html>
    <head>
        <title>Finding the length of arrays and strings</title>
        <script src="script.js"></script>
    </head>
        
    <body>

    </body>
</html>

And here is the sample JavaScript code:

// Create an array
var cars = ["BMW", "Volkswagen", "Toyota", "Audi"];

// Use the length method to find the length of the array
// The length of an array is the number of elements it contains
var numberofcars = cars.length;
console.log(numberofcars);

// Create a string
var password = "oranges";

// Use the length method to find the length of the string
// The length of a string is how many characters it contains
var passwordlength = password.length;
console.log(passwordlength);

// We can also find the length of an individual string element in an array
// by referring to the index of the element
console.log(cars[1].length);

Next tutorial: Multidimensional arrays

Leave a Reply