**Constants** are similar to variables however their value, as expressed by the name, is always **constant** or **unchanged**.

We can declare a constant using the const keyword, and it's important to initialize it at the same point as well. Following is the syntax for constant declaration & initialization:
```js
const constantName = data;
```

For example:
```js
const exampleConstant = 123;
```

Changing the value of a constant results in an error:
```js
const exampleConstant = 123;
exampleConstant = 1234; // Error here
```

The names of the constants follow the same naming rules as the variables.


Which keyword is used to declare a constant in JavaScript?

What happens if you try to reassign a value to a constant?

Which of the following correctly declares and initializes a constant in a single **statement**?

In this section, we will get an introduction to JavaScript by looking at the basic syntax of the language, along with a few terms and concepts which will build our foundation for learning more advanced features of the language in the upcoming section. This section will include hands-on tasks which will help you practice all the concepts and remember the contents naturally without effort.

In this section, we will look at how to store some data and retrieve it later on using Variables. Moreover, we will explore some basic data types and look at how they interact with each other.

In this chapter we will look at how to write expressions which evaluate to "true" or "false" based on the conditions, for example "Is X equal to Y?". Afterwards, we will build on that concept and learn to write "Conditional Statements" which will enable us to conditionally execute specific lines of code.

Introduction to JavaScript

Constants

1. What is a constant in JavaScript?

2. Which keyword is used to declare a constant in JavaScript?

3. What happens if you try to reassign a value to a constant?

4. Which of the following correctly declares and initializes a constant in a single statement?