JavaScript

Content

1. Chapter 1: The JavaScript Language
   • Chapter 1 - Part 1: First Program in JavaScript
   • Chapter 1 - Part 2: Variables Types in JavaScript
   • Chapter 1 - Part 3: Data Output in JavaScript
   • Chapter 1 - Part 4: Data Processing in JavaScript
   • Chapter 1 - Part 5: Data Casting in JavaScript
   • Chapter 1 - Part 6: Data Input in JavaScript
   • Chapter 1 - Part 7: Conditional Statement in JavaScript
   • Chapter 1 - Part 8: While Statement in JavaScript
   • Chapter 1 - Part 9: For Statement in JavaScript
   • Chapter 1 - Part 10: Vectors in JavaScript
   • Chapter 1 - Part 11: Matrix in JavaScript
2. Chapter 2: Object Oriented
   • Chapter 2 - Part 1: Abstraction
   • Chapter 2 - Part 2: Encapsulation
   • Chapter 2 - Part 3: Inheritance
   • Chapter 2 - Part 4: Polymorphism

Chapter 1: The JavaScript Language

Chapter 1 - Part 1: First Program in JavaScript

console.log('Hello World');

Chapter 1 - Part 2: Variables Types in JavaScript

var x;
let y;

Both var and let are used to declare variables. However, there are some differences between them.

var	let
var is used in the older versions of JavaScript	let is the new way of declaring variables starting ES6 (ES2015).
var is function scoped (will be discussed in later tutorials).	let is block scoped (will be discussed in later tutorials).
For example, var x;	For example, let y;

let x;
x = 5;

console.log(x);

y = 6, z = 7;

console.log(y);
console.log(z);

The const keyword was also introduced in the ES6(ES2015) version to create constants.

const x = 5;

Once a constant is initialized, we cannot change its value.

const x = 5;
x = 10;  // Error! constant cannot be changed.
console.log(x)

Data Types	Description	Example
String	Represents textual data	'hello', "hello world!" etc
Number	An integer or a floating-point number	3, 3.234, 3e-2 etc.
BigInt	An integer with arbitrary precision	900719925124740999n , 1n etc.
Boolean	Any of two values: true or false	true and false
undefined	A data type whose variable is not initialized	let a;
null	Denotes a null value	let a = null;
Symbol	Data type whose instances are unique and immutable	let value = Symbol('hello');
Object	key-value pairs of collection of data	let student = { };

Chapter 1 - Part 3: Data Output in JavaScript

Chapter 1 - Part 4: Data Processing in JavaScript

Chapter 1 - Part 5: Data Casting in JavaScript

Chapter 1 - Part 6: Data Input in JavaScript

Chapter 1 - Part 7: Conditional Statement in JavaScript

Chapter 1 - Part 8: While Statement in JavaScript

Chapter 1 - Part 9: For Statement in JavaScript

Chapter 1 - Part 10: Vectors in JavaScript

Chapter 1 - Part 11: Matrix in JavaScript

Chapter 2: Object Oriented

Chapter 2 - Part 1: Abstraction

How it represents a real object in our system. It must have identity (Class) given by properties (attributes) and methods (functions).

o Class: Structured type that can contain members - Representation of an entity (Product, Customer), service (ProductService, CustomerService), drivers (ProductController), utilities (calculator) and others (views, repositories). o Attributes (Data or Fields - Ex: Customer has attribute name, email, cpf and etc.) o Methods (Class functions and operations - Ex: Consult email, consult cpf, change cpf)

• A class can also have: o Constructors (Special class operation, performed at instantiation of the class. Used to start attribute values ​​or to force the object to receive data or dependency on its instantiation (Dependency injection)) o Overload of constructors or methods (Esoecify more than one constructor or method in the class) Encapsulation (Getters and Setters) o Inheritance (from whom this class inherits) Polymorphism (A class has several forms or functions)

• Object: They are the instance of the class or instance of the type - Ex: Product p1, Client customer1 • Class: It is the definition of the type (Customer Class, Product Class)

• Instantiation: When we instantiate primitive variables (double, int, String ...) it is instantiated in the memory stack. When the command New in Objects, Arrays and Lists is communicated, the dynamic location of memory occurs, where the object is allocated in another area of memory, called Heap and the object will point to the memory address.

• Advantages of object orientation: o Reuse of the code and delegation of responsibilities

Chapter 2 - Part 2: Encapsulation

Adds security to an object-oriented application, as it hides class properties.

o An object must not expose any attributes (use of access modifiers - private, protected ...) o Class attributes are usually accessed by special methods (Getters and Setters), avoiding direct access to the object's property. o Analogy with a television: When you click on the call button, we do not know what happens internally on the TV. We can say that the methods that connect the TV are encapsulated.

Chapter 2 - Part 3: Inheritance

Type of association between classes that allows a class to inherit all data and behavior from another

o Can be used for code reuse o Used for polymorphism - A class has several uses The whole class java me, inherits from Object (Warper Classes)

Chapter 2 - Part 4: Polymorphism

A feature that allows variables of the same more generic type to be able to point to objects of different specific types, thus having different behaviors according to each specific type. In some cases, we must perform the upcasting or dowcasting of the object.