| 24 | [Mini Projeto: Sistema Solar](./24_Day_Project_solar_system/24_day_project_solar_system.md) |
| 25 | [Mini Projeto: Visualização de Dados de Paises do mundo](./25_Day_World_countries_data_visualization_1/25_day_world_countries_data_visualization_1.md) |
| 26 | [Mini Projeto: Visualização de Dados de Paises do mundo 2](./26_Day_World_countries_data_visualization_2/26_day_world_countries_data_visualization_2.md) |
- [Introdução Tipo de Dados](#introduction-to-data-types)
- [Números](#numbers)
- [Strings](#strings)
- [Booleanos](#booleans)
- [Undefined](#undefined)
- [Null](#null)
- [Verificando Tipo de Dados](#checking-data-types)
- [Novamente Comentarios](#comments-again)
- [Variáveis](#variables)
- [💻 Dia 1: Exercícios](#-day-1-exercises)
# 📔 Dia 1
## Introdução
**Parabéns** Em decidir participar dos 30 dias de JavaScript desafio. Neste desafio você aprenderá tudo que precisa para ser um JavaScript programador, e em general, todo o conceito de programaçao. No fim do desafio voce estará adquirindo o Certificado de conclusão dos 30DiasdeJavaScript desafio. Em caso de precisar de ajuda ou se preferir ajudar outros você pode entrar no [Grupo Telegram](https://t.me/ThirtyDaysOfJavaScript).
**30DiasDeJavaScript** desafio é um guia tanto para iniciantes e Avançados JavaScript Desenvolvedores, Bem vindo ao JavaScript. JavaScript é a linguagem da internet. Eu me divirto em usar e ensinar JavaScript e eu acredito que voce fará tambem.
Neste passo a passo do JavaScript Desafio, você aprenderá JavaScript, a mais popular linguagem de programação da história da humanindade.
JavaScript é usado **_para adicionar interatividade aos websites, desenvolvimento de mobile apps, desktop aplicações, jogos_** e nos dias de hoje JavaScript pode ser usado para **_machine learning_** e **_AI_**.
**_JavaScript (JS)_** Teve um aumento na popularidade nos últimos anos e segue como a linguagem de programação líder por seis anos consecutivos e é a linguagem de programação mais usada no GitHub
## Requisitos
Sem conhecimentos prévios de programação é exigido para seguir este desafio. Precisará apenas:
1. Motivação
2. Um computador
3. Internet
4. Um navegador
5. Um editor de Código
## Setup
Eu acredito que voce tem a motivação e o forte desejo de ser um desenvolvedor, um computador e internet. Se voce tem isso, então você tem tudo para iniciar.
## Instalando Node.js
Você pode não precisar do Node.js agora mas você precisará mais tarde. Instalação do [node.js](https://nodejs.org/en/).
Nós podemos verificar se o Node está instalador na nossa máquina local abrindo nosso terminal do dispositivo ou prompt de comando.
```sh
asabeneh $ node -v
v12.14.0
```
Enquanto fazia este tutorial eu estava usando a versão 12.14.0 do Node, mas agora a recomendada versão do Node.js para dowload é v14.17.6, pelo tempo que você usar este material pode haver versão mais atual do Node.js.
### Navegador
Existe muitos navegadores por ai, Entento, Eu fortemente recomento o Google Chrome.
#### Instalando Google Chrome
Instalar o [Google Chrome](https://www.google.com.br/chrome/) se você não tem um ainda. Nós podemos escrever um pequeno código de JavaScript no console do browser, mas nós não usamos o console do navegador para desenvolver aplicações.
Você pode abrir o Google Chrome console por um ou outro clicando nos 3 pontos no topo do lado direito do navegador, selecionando _Mais ferramentas -> Ferramenta para desenvolvedores ou usando o atalho do teclado. Eu prefiro os atalhos.
After you open the Google Chrome console, try to explore the marked buttons. We will spend most of the time on the Console. The Console is the place where your JavaScript code goes. The Google Console V8 engine changes your JavaScript code to machine code.
Let us write a JavaScript code on the Google Chrome console:
#### Writing Code on Browser Console
We can write any JavaScript code on the Google console or any browser console. However, for this challenge, we only focus on Google Chrome console. Open the console using:
```sh
Mac
Command+Option+I
Windows:
Ctl+Shift+I
```
##### Console.log
To write our first JavaScript code, we used a built-in function **console.log()**. We passed an argument as input data, and the function displays the output. We passed `'Hello, World'` as input data or argument in the console.log() function.
```js
console.log('Hello, World!')
```
##### Console.log with Multiple Arguments
The **`console.log()`** function can take multiple parameters separated by commas. The syntax looks like as follows:**`console.log(param1, param2, param3)`**
As you can see from the snippet code above, _`console.log()`_ can take multiple arguments.
Congratulations! You wrote your first JavaScript code using _`console.log()`_.
##### Comments
We can add comments to our code. Comments are very important to make code more readable and to leave remarks in our code. JavaScript does not execute the comment part of our code. In JavaScript, any text line starting with // in JavaScript is a comment, and anything enclosed like this `//` is also a comment.
**Example: Single Line Comment**
```js
// This is the first comment
// This is the second comment
// I am a single line comment
```
**Example: Multiline Comment**
```js
/*
This is a multiline comment
Multiline comments can take multiple lines
JavaScript is the language of the web
*/
```
##### Syntax
Programming languages are similar to human languages. English or many other language uses words, phrases, sentences, compound sentences and other more to convey a meaningful message. The English meaning of syntax is _the arrangement of words and phrases to create well-formed sentences in a language_. The technical definition of syntax is the structure of statements in a computer language. Programming languages have syntax. JavaScript is a programming language and like other programming languages it has its own syntax. If we do not write a syntax that JavaScript understands, it will raise different types of errors. We will explore different kinds of JavaScript errors later. For now, let us see syntax errors.
I made a deliberate mistake. As a result, the console raises syntax errors. Actually, the syntax is very informative. It informs what type of mistake was made. By reading the error feedback guideline, we can correct the syntax and fix the problem. The process of identifying and removing errors from a program is called debugging. Let us fix the errors:
```js
console.log('Hello, World!')
console.log('Hello, World!')
```
So far, we saw how to display text using the _`console.log()`_. If we are printing text or string using _`console.log()`_, the text has to be inside the single quotes, double quotes, or a backtick.
**Example:**
```js
console.log('Hello, World!')
console.log("Hello, World!")
console.log(`Hello, World!`)
```
#### Arithmetics
Now, let us practice more writing JavaScript codes using _`console.log()`_ on Google Chrome console for number data types.
In addition to the text, we can also do mathematical calculations using JavaScript. Let us do the following simple calculations.
It is possible to write JavaScript code on Google Chrome console can directly without the **_`console.log()`_** function. However, it is included in this introduction because most of this challenge would be taking place in a text editor where the usage of the function would be mandatory. You can play around directly with instructions on the console.
We can write our codes on the browser console, but it won't be for bigger projects. In a real working environment, developers use different code editors to write their codes. In this 30 dias de JavaScript challenge, we will be using Visual Studio Code.
#### Installing Visual Studio Code
Visual Studio Code is a very popular open-source text editor. I would recommend to [download Visual Studio Code](https://code.visualstudio.com/), but if you are in favor of other editors, feel free to follow with what you have.
If you installed Visual Studio Code, let us start using it.
#### How to Use Visual Studio Code
Open the Visual Studio Code by double-clicking its icon. When you open it, you will get this kind of interface. Try to interact with the labeled icons.
JavaScript can be added to a web page in three different ways:
- **_Inline script_**
- **_Internal script_**
- **_External script_**
- **_Multiple External scripts_**
The following sections show different ways of adding JavaScript code to your web page.
### Inline Script
Create a project folder on your desktop or in any location, name it 30DaysOfJS and create an **_`index.html`_** file in the project folder. Then paste the following code and open it in a browser, for example [Chrome](https://www.google.com/chrome/).
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>30DaysOfScript:Inline Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DiasDeJavaScript!')">Click Me</button>
</body>
</html>
```
Now, you just wrote your first inline script. We can create a pop up alert message using the _`alert()`_ built-in function.
### Internal Script
The internal script can be written in the _`head`_ or the _`body`_, but it is preferred to put it on the body of the HTML document.
First, let us write on the head part of the page.
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>30DaysOfScript:Internal Script</title>
<script>
console.log('Welcome to 30DiasDeJavaScript')
</script>
</head>
<body></body>
</html>
```
This is how we write an internal script most of the time. Writing the JavaScript code in the body section is the most preferred option. Open the browser console to see the output from the `console.log()`.
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>30DaysOfScript:Internal Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DiasDeJavaScript!');">Click Me</button>
<script>
console.log('Welcome to 30DiasDeJavaScript')
</script>
</body>
</html>
```
Open the browser console to see the output from the `console.log()`.
### External Script
Similar to the internal script, the external script link can be on the header or body, but it is preferred to put it in the body.
First, we should create an external JavaScript file with .js extension. All files ending with .js extension are JavaScript files. Create a file named introduction.js inside your project directory and write the following code and link this .js file at the bottom of the body.
```js
console.log('Welcome to 30DiasDeJavaScript')
```
External scripts in the _head_:
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>30DiasDeJavaScript:External script</title>
<scriptsrc="introduction.js"></script>
</head>
<body></body>
</html>
```
External scripts in the _body_:
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>30DiasDeJavaScript:External script</title>
</head>
<body>
<!-- JavaScript external link could be in the header or in the body -->
<!-- Before the closing tag of the body is the recommended place to put the external JavaScript script -->
<scriptsrc="introduction.js"></script>
</body>
</html>
```
Open the browser console to see the output of the `console.log()`.
### Multiple External Scripts
We can also link multiple external JavaScript files to a web page.
Create a `helloworld.js` file inside the 30DaysOfJS folder and write the following code.
```js
console.log('Hello, World!')
```
```html
<!DOCTYPE html>
<htmllang="en">
<head>
<title>Multiple External Scripts</title>
</head>
<body>
<scriptsrc="./helloworld.js"></script>
<scriptsrc="./introduction.js"></script>
</body>
</html>
```
_Your main.js file should be below all other scripts_. It is very important to remember this.
## Introduction to Data types
In JavaScript and also other programming languages, there are different types of data types. The following are JavaScript primitive data types: _String, Number, Boolean, undefined, Null_, and _Symbol_.
### Numbers
- Integers: Integer (negative, zero and positive) numbers
Example:
... -3, -2, -1, 0, 1, 2, 3 ...
- Float-point numbers: Decimal number
Example
... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...
### Strings
A collection of one or more characters between two single quotes, double quotes, or backticks.
**Example:**
```js
'a'
'Asabeneh'
"Asabeneh"
'Finland'
'JavaScript is a beautiful programming language'
'I love teaching'
'I hope you are enjoying the first day'
`We can also create a string using a backtick`
'A string could be just as small as one character or as big as many pages'
'Any data type under a single quote, double quote or backtick is a string'
```
### Booleans
A boolean value is either True or False. Any comparisons returns a boolean value, which is either true or false.
A boolean data type is either a true or false value.
**Example:**
```js
true // if the light is on, the value is true
false // if the light is off, the value is false
```
### Undefined
In JavaScript, if we don't assign a value to a variable, the value is undefined. In addition to that, if a function is not returning anything, it returns undefined.
```js
let firstName
console.log(firstName) // undefined, because it is not assigned to a value yet
```
### Null
Null in JavaScript means an empty value.
```js
let emptyValue = null
```
## Checking Data Types
To check the data type of a certain variable, we use the **typeof** operator. See the following example.
```js
console.log(typeof 'Asabeneh') // string
console.log(typeof 5) // number
console.log(typeof true) // boolean
console.log(typeof null) // object type
console.log(typeof undefined) // undefined
```
## Comments Again
Remember that commenting in JavaScript is similar to other programming languages. Comments are important in making your code more readable.
There are two ways of commenting:
- _Single line commenting_
- _Multiline commenting_
```js
// commenting the code itself with a single comment
// let firstName = 'Asabeneh'; single line comment
// let lastName = 'Yetayeh'; single line comment
```
Multiline commenting:
```js
/*
let location = 'Helsinki';
let age = 100;
let isMarried = true;
This is a Multiple line comment
*/
```
## Variables
Variables are _containers_ of data. Variables are used to _store_ data in a memory location. When a variable is declared, a memory location is reserved. When a variable is assigned to a value (data), the memory space will be filled with that data. To declare a variable, we use _var_, _let_, or _const_ keywords.
For a variable that changes at a different time, we use _let_. If the data does not change at all, we use _const_. For example, PI, country name, gravity do not change, and we can use _const_. We will not use var in this challenge and I don't recommend you to use it. It is error prone way of declaring variable it has lots of leak. We will talk more about var, let, and const in detail in other sections (scope). For now, the above explanation is enough.
A valid JavaScript variable name must follow the following rules:
- A JavaScript variable name should not begin with a number.
- A JavaScript variable name does not allow special characters except dollar sign and underscore.
- A JavaScript variable name follows a camelCase convention.
- A JavaScript variable name should not have space between words.
The following are examples of valid JavaScript variables.
```js
firstName
lastName
country
city
capitalCity
age
isMarried
first_name
last_name
is_married
capital_city
num1
num_1
_num_1
$num1
year2020
year_2020
```
The first and second variables on the list follows the camelCase convention of declaring in JavaScript. In this material, we will use camelCase variables(camelWithOneHump). We use CamelCase(CamelWithTwoHump) to declare classes, we will discuss about classes and objects in other section.
Example of invalid variables:
```js
first-name
1_num
num_#_1
```
Let us declare variables with different data types. To declare a variable, we need to use _let_ or _const_ keyword before the variable name. Following the variable name, we write an equal sign (assignment operator), and a value(assigned data).
```js
// Syntax
let nameOfVariable = value
```
The nameOfVriable is the name that stores different data of value. See below for detail examples.
**Examples of declared variables**
```js
// Declaring different variables of different data types
let firstName = 'Asabeneh' // first name of a person
let lastName = 'Yetayeh' // last name of a person
let country = 'Finland' // country
let city = 'Helsinki' // capital city
let age = 100 // age in years
let isMarried = true
console.log(firstName, lastName, country, city, age, isMarried)
```
```sh
Asabeneh Yetayeh Finland Helsinki 100 true
```
```js
// Declaring variables with number values
let age = 100 // age in years
const gravity = 9.81 // earth gravity in m/s2
const boilingPoint = 100 // water boiling point, temperature in °C
const PI = 3.14 // geometrical constant
console.log(gravity, boilingPoint, PI)
```
```sh
9.81 100 3.14
```
```js
// Variables can also be declaring in one line separated by comma, however I recommend to use a seperate line to make code more readble
let name = 'Asabeneh', job = 'teacher', live = 'Finland'
console.log(name, job, live)
```
```sh
Asabeneh teacher Finland
```
When you run _index.html_ file in the 01-Day folder you should get this:
🌕 You are amazing! You have just completed day 1 challenge and you are on your way to greatness. Now do some exercises for your brain and muscle.
# 💻 Day 1: Exercises
1. Write a single line comment which says, _comments can make code readable_
2. Write another single comment which says, _Welcome to 30DiasDeJavaScript_
3. Write a multiline comment which says, _comments can make code readable, easy to reuse_
_and informative_
4. Create a variable.js file and declare variables and assign string, boolean, undefined and null data types
5. Create datatypes.js file and use the JavaScript **_typeof_** operator to check different data types. Check the data type of each variable
6. Declare four variables without assigning values
7. Declare four variables with assigned values
8. Declare variables to store your first name, last name, marital status, country and age in multiple lines
9. Declare variables to store your first name, last name, marital status, country and age in a single line
10. Declare two variables _myAge_ and _yourAge_ and assign them initial values and log to the browser console.
