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Introduction

Course Overview

Introduction to JavaScript

JavaScript Basics

JavaScript - Hello World

JavaScript - Comments

Quiz

JavaScript Variables and Operators

JavaScript - Variables

JavaScript - Operators

Quiz

JavaScript Conditionals

Introduction to Conditional Statements in JavaScript

JavaScript - If...Else

JavaScript - Switch Case

Quiz

JavaScript Objects

Introduction to Objects in JavaScript

JavaScript - Number

JavaScript - Boolean

JavaScript - Math

JavaScript - Date

Quiz

JavaScript - Functions

Introductions to Function in JavaScript

JavaScript - Variable Scope

JavaScript - Default Parameters

JavaScript - Arrow Functions

Quiz

JavaScript - String and Arrays

Introduction to Strings in JavaScript

JavaScript - String Methods

Introduction to Array in JavaScript

JavaScript - Array Methods

Quiz

JavaScript Loops

Introduction to loops in JavaScript

JavaScript - for loop

JavaScript - while loop

JavaScript - do-while loop

JavaScript - for-in loop

JavaScript - for-of loop

JavaScript - Loop Control

Quiz

JavaScript - Maps and Sets

JavaScript - Maps

JavaScript - Sets

Quiz

Conclusion

Where to Go from Here

JavaScript - Variables

What are Variables?

In programming, variables are used to store information that can be used later in your code. Think of a variable as a container that holds data. You can name this container anything you like, and then use that name to access the data stored in it.

Types of Variables

In JavaScript, there are three ways to declare a variable:

var
let
const

For now, we'll focus on var to keep things simple.

Declaring a Variable

To create a variable, you need to declare it. Declaring a variable means telling the program that this container exists and giving it a name. Here's how you declare a variable using var:

var myVariable;

This line of code creates a variable named myVariable. Right now, myVariable doesn't contain any data. Let's give it some data!

Assigning a Value to a Variable

You can assign a value to a variable when you declare it, or you can do it later. Here's how you do it:

var myVariable = 10;

You can also do it in two steps:

var myVariable;
myVariable = 10;

Using Variables

Once you've created a variable and assigned it a value, you can use it in your code. For example, you can print the value of myVariable to the console. When you run this code, it will print 10 to the console.

Javascript

. . . .

Changing the Value of a Variable

One of the powerful features of variables is that you can change their value. Here's an example:

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. . . .

In this example, myVariable starts with the value 10. Then, we change its value to 20. When we print it again, it shows the new value.

Example: Using Variables in a Simple Program

Variables can store numbers as well as strings (and other types that we will discuss later). Here is an example using variables with strings stored in them.

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. . . .

In this program, we create two variables: greeting and theName. We assign the values "Hello" and "World" to them. Then, we use the + operator to combine these values and print "Hello World" to the console.

Quiz

JavaScript - Operators

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On this page

What are Variables?

Types of Variables

Declaring a Variable

Assigning a Value to a Variable

Using Variables

Changing the Value of a Variable

Example: Using Variables in a Simple Program