Course Content

Introduction to JavaScript (staging)

1. Introduction

Writing our first code Output Using Variables 1/2 Output Using Variables 2/2

2. JavaScript syntax

JavaScript Syntax JavaScript Variables JavaScript Operators Identifiers in JavaScript Naming Identifiers Reserved keywords in JavaScript Naming Convention in JavaScript. Case Styles Variables Naming Convention Boolean Naming Convention Constant Naming Convention Function & Classes Naming Convention Multiline Strings Multiline Strings. Concatenating Commenting in JavaScript Commenting in JavaScript. Multi-line Comments

Var 1/3

Var:

In the very first chapter of the section we learn that there are three ways to declare a variable:

let
const
var

The var is used as an alternative to the let keyword. We can replace let with the var or vice-versa but there are some exceptions.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Var has No Block Scope

Variables have either local-scope or global-scope. The code which is enclosed inside the {} is called a block of code. Variables declared with var are accessible outside the block as well, for example.


              1234
            
if (10 > 5){
    var test = true;
}
console.log(test);

But if we declare the test variable with the let keyword we get an error.


              1234
            
if (10 > 5){
    let test = true;
}
console.log(test);

As you can see that the test variable was accessible outside the if statement when declared with the var keyword, but it was not accessible when declared with the let keyword.

Note: Scoping is an advanced topic therefore this part has no exercise because we will learn more about the scope in the upcoming chapters.

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 3. Chapter 4

Var 1/3

Var:

In the very first chapter of the section we learn that there are three ways to declare a variable:

let
const
var

The var is used as an alternative to the let keyword. We can replace let with the var or vice-versa but there are some exceptions.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Var has No Block Scope


              1234
            
if (10 > 5){
    var test = true;
}
console.log(test);

But if we declare the test variable with the let keyword we get an error.


              1234
            
if (10 > 5){
    let test = true;
}
console.log(test);

As you can see that the test variable was accessible outside the if statement when declared with the var keyword, but it was not accessible when declared with the let keyword.

Note: Scoping is an advanced topic therefore this part has no exercise because we will learn more about the scope in the upcoming chapters.

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 3. Chapter 4

Var 1/3

Var:

In the very first chapter of the section we learn that there are three ways to declare a variable:

let
const
var

The var is used as an alternative to the let keyword. We can replace let with the var or vice-versa but there are some exceptions.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Var has No Block Scope


              1234
            
if (10 > 5){
    var test = true;
}
console.log(test);

But if we declare the test variable with the let keyword we get an error.


              1234
            
if (10 > 5){
    let test = true;
}
console.log(test);

As you can see that the test variable was accessible outside the if statement when declared with the var keyword, but it was not accessible when declared with the let keyword.

Note: Scoping is an advanced topic therefore this part has no exercise because we will learn more about the scope in the upcoming chapters.

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Var:

In the very first chapter of the section we learn that there are three ways to declare a variable:

let
const
var

The var is used as an alternative to the let keyword. We can replace let with the var or vice-versa but there are some exceptions.

Task

Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.

Var has No Block Scope


              1234
            
if (10 > 5){
    var test = true;
}
console.log(test);

But if we declare the test variable with the let keyword we get an error.


              1234
            
if (10 > 5){
    let test = true;
}
console.log(test);

As you can see that the test variable was accessible outside the if statement when declared with the var keyword, but it was not accessible when declared with the let keyword.

Note: Scoping is an advanced topic therefore this part has no exercise because we will learn more about the scope in the upcoming chapters.

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Section 3. Chapter 4

Switch to desktop for real-world practiceContinue from where you are using one of the options below