JavaScript Variables

A variable contains a value. When you use the variable, you refer to the data it represents. You use variables to store, retrieve and manipulate values in your code.

Declaring Variables

In the declaration it's where a variable appears in the script for the first time. The declaration sets it up in the memory so that you can refer to it in your script. A variable should be declared before start using it. To declare it you will do this by using the var keyword.

JavaScript - Declaring variables

<!DOCTYPE html>
        <h2>JavaScript Variables</h2>
        <p id="variablesdemo"></p>
        // A single declaration.
        var x;
        // Multiple declarations with a single var keyword.
        var x, y, z;
        // Variable declaration and initialization in one statement.
        var x = 0, y = 100;
        var z = 234;
        var x = 5;
        var y = 6;
        // Let's do some calculation.
        z = y * x;
        document.getElementById("variablesdemo").innerHTML = "The value of z is: " + z;

Learn more about JavaScript Var Learn more about JavaScript Let

Naming Variables

Like many other programming languages also JavaScript is case-sensitive. That means that the variable oldCar is not the same variable as the variable OLDCar. A variable name can consist of any number of characters. There are some rules to be followed when we create a legal variable name:

  • It's required to use an ASCII letter as the first character, it can be either an uppercase or a lowercase. It must comply with Unicode variable naming conventions or it can be an underscore (_) character. Note that a number cannot be used as the first character.
  • All subsequent characters must be either letters, numbers, or underscores (_).
  • The variable name cannot be a reserved word.

Example of legal variable names:

var _oldDog
var OldDog
var old_Dog

Example of illegal variable names:

// Cannot begin with a number.
var 55old_Dogs

// The ampersand (&) character is not a valid character for variable names.
var Old & Dog

When a variable is declare and initialized it can be assigned to the value null. This is done if you don't want to give it any particular value.
Here is an example:

var x = null;
var y = 3 * x;  // y = 0

When a variable is declared without assigning a value to it, it will have the value undefined.

Take a look at this example:

var x;
// y will have the value NaN because x is undefined.
var y = 1 * x;
// Result: NaN

When a variable is declared without using the var keyword in the declaration, we call that an implicit declaration. It is possible to assign a value to it at the same time.

// Here the variable x is declared implicitly.
x = "";
// This will return an empty result.

It is not possible to use a variable that is not declared. That will cause an error.

// This will cause an error since the variables are not declared and do not exist.
var x = a * b;


JavaScript is a loosely typed language and that means that JavaScript variables have no predetermined type. The type of a variable will be the same as the type of of its value. Because of this you can treat a value as if it were of a different type.

JS JavaScript - Coercion

var x = 2000;
var y = "Hello";
// The number is coerced to a string.
x = x + y;
// Output:
// 2000Hello

Learn more about JavaScript Comments Learn more about JavaScript Scope

Check this out

JS JavaScript: Dates

Date and Time are used in our everyday lives. It is important to understand how to use Date and Time in computer programming. You might have to create a website with a calendar. The application should show relevant times based on the user's current timezone. 

JavaScript offers us a d....

JS JavaScript: Array Sort

The sort() method in JavaScript is sorting the elements in an array and will return the sorted array. The default sort order is according to string Unicode code points.

JS JavaScript: Errors

There will be errors in the code. It is good practice to handle exceptions/errors.

Exceptions are a type of error that occurs during the execution of an application. Errors should be logged. Sometimes it is possible to recover a bug and proceed.
Other cases the user should get inform....

JS JavaScript: Math Object

JavaScript Math object enables mathematical tasks on numbers. 
The properties and methods of Math are static and can be called without creating the Math object.


JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:

1.      HTML to define the content of web pages.

2.      CSS to specify the layout of web pages.

3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.

The benefits of using JavaScript are:

1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.


Need more Honney

NDC Conferences

The NDC Conferences (Norwegian Developers Conference) are one of the world`s largest independent software conferences for .NET & Agile development. The conference covers everything you need to know within software development. The conferences are held each year in many places such as Oslo, Copenhagen, London, Sydney and Minnesota.

Update Conference Prague

Update Conference Prague is the biggest developer conference in the Czech Republic. The conference is offering sessions delivered by the top experts from all around the world. Their goal is to inspire the attendees and enrich their knowledge.

Troy Hunt

Learn about Web Security from Troy Hunt. He is a really engaged speaker that frequently give talks on conferences around the world. Troy is a Microsoft MVP and you can even learn from him on some great courses on Pluralsight.

W3Schools is a great education Web Site for learning web technologies. On W3Schools you may find well organized basic to advanced tutorials and references.

Scott Hanselman

Learn about Web Technologies and new trends from Scott Hanselman. Scott Hanselman is an author of developer books and he is an engaged speaker that usually talks about the Microsoft stack. You may meet Scott on conferences around the world.

Developer Week

DeveloperWeek is one of the world’s largest developer conferences. Developer Week focus on new dev technologies, the conference have talks and workshops for newbies and experienced audience. You can attend on a Developer Week conference different places in Nothern America.


Honneybag blog

Learn JavaScript Debugging

Searching for bugs and fixing them is called code debugging. The bugs might be difficult to diagnose and therefore it is important to have a good approach to find and fix the bugs effectively. Bugs in the code might be syntax errors or logical errors. Sometimes nothing happens when the code contains bugs and there is few indications where to search. Modern web browser includes a powerful suite of developer tools. The tools do a range of things...

Explore JavaScript Arrays

Arrays are frequently used by developers. Programming languages can have slightly different implementation of arrays. An array is an object that can store a collection of items. You may say it`s a special variable that can have more than one value. The array holds many values under a single name, and you may access the values by referring to an index number. The easiest way to create....

Ultimate Guide to HTML Colors

It is essential to give the user a good user experience. There are many things you should focus on, one of them is how you use colors on your website. We don't have to struggle with black and white TVs anymore. Users expect more and more and we can apply colors to everything we want. Texts, borders, backgrounds, shadows – in HTML they all can have whatever color you decide....

Wanna be a sheep? Check out the most popular subjects
Wanna be a little different? Check out the less popular subjects