path: root/TypeScript/ts-testing.ts

// Notes taken from: https://www.youtube.com/watch?v=NjN00cM18Z4 and https://www.youtube.com/watch?v=xPEMup5SPTM

/*******************/
/* Variable scopes */
/*******************/

function doSmth() {
	if (true) {
		// With "var" the scope is the nearest function
		var variable = 1;
	}
	console.log(variable);

	if (true) {
		// With "let" the socope is the nearest block
		let anotherVariable = 2;
	}

	// The following line shows you an error
	// IMPORTANT: if you build it with the following line uncommented, 
	// tsc will give you an error, but will make let anotherVariable to var anotherVariable in the js file

	// console.log(anotherVariable)
}

/***********************/
/* Declaring variables */
/***********************/

// Declaring a variable and initializing (giving it a value when declared)
// will cast the value to a specific data type (doesn't matter if you use "let" or "var")
var num  = 5;
let num1 = -5;
let arr = [1, 2, 3]; // declare an initilize an int array
num  = 16;
num1 = -16;
arr = [5, 6, 7];

// The following two lines give you an error, if uncommented

// num  = "Hello";
// num1 = "Hello";
// arr = ["Hello", "World"];

// Declaring a variable without initializing it will give it the type "any",
// meaning it can be assigned whatever type of value
let anyVariable;
anyVariable = 16;
anyVariable = "Hello";
anyVariable = true;

/****************************/
/* Declaring variable types */
/****************************/

// This is how to declare variables of given type (without initializing)
let myNum: number; // no difference between doubles, ints, longs, ...
let myBool: boolean;
let myString: string;
let myAny: any;

// This is how to declare arrays (without initializing)
let myNumArray: number[];
let myAnyArray: any[];

// Note: you can also initilize an array when declaring it
let numArray: number[] = [1, 2, 3];
// but in this case TypeScript will take care of data type for you,
// so you can simplify it to this
let numArray1 = [1, 2, 3];

// You can declare that a variable can be multiple types with the pipe (|) symbol
let myNumOrString: number | string;
// You can also use as many as you like
let myNumOrStringOrBool: number | string | boolean;
// You can also apply this to arrays
let myNumOrStringArray: (number | string)[];

// Declaring enums (the same way as in C#)

enum ColorCodes {
	Red = 0,
	Green = 1,
	Blue = 2
}

// Type insertion: when you tell the compiler that a given value is of given type

let message;
message = "Hello World";

// Because message isn't initilized, it's type is "any"
// but when we want to do something like this, intellisense won't tell you that 
// the string function "charAt" is available (but the code will compile just fine)
let firstCharInMessage = message.charAt(0);

// If we want to get help in situations, where the type is "any",
// but we want a function of a specific type, we can do type insertion
firstCharInMessage = (<string>message).charAt(0);
// you can also do it like this, both ways work the same, it's up to preference which one to use
firstCharInMessage = (message as string).charAt(0);

/*************/
/* Functions */
/*************/

// Note: methods are functions inside objects, in C# everything is an object, so we have only methods there, but in TypeScript it isn't like that
function add(num1, num2) {
	return num1 + num2;
}
// You can declare parameter data types
function add1(num1: number, num2: number) {
	return num1 + num2;
}
// You can also declare the return type
function add2(num1: number, num2: number): number {
	return num1 + num2;
}

// Let's say you want to assign a function to a variable
// In Javascript you're gonna do it like this
let myFunction = function () {
	console.log("Test");
}

// Well, in TypeScript, you can do the same with an arrow function, that
// is equavalent to the C# lambda function
myFunction = () => console.log("Test");
// You can also add a body to it
myFunction = () => {
	console.log("Test");
}
// And you can add parameters
let myOtherFunction = (message) => {
	console.log(message);
}

/******************/
/* Custom objects */
/******************/

// You can easily create objects with any properties with curly brackets
let myObject = {
	Name: "Pesho",
	Age: 20,
	Married: false
}

// If you want to give an object as a function parameter
let drawPoint = (pointLocation) => {
	// ...
}
// you can do it like this, without having a class/interface (DON'T do this)
drawPoint({ x: 1, y: 3 });

// But to make sure that the given object has some proerties, we can do 
// inline annotation in our function
// This declares that pointLocation's type is an object, that has two number properties: x and y
drawPoint = (pointLocation: { x: number, y: number }) => {
	// ...
}

/*******************************/
/* Object oriented programming */
/*******************************/

// Making an interface
interface IPerson {
	name: string,
	age: number,
	married: boolean,
	eat: (food) => void // this is how to declare a function type
}

// Making a class
class Person {
	name: string;
	age: number;
	married: boolean;

	constructor(name: string, age: number, married?: boolean) {
		this.name = name;
		this.age = age;
		// The married? means the married variable is optional, you don't need to give it a value
		this.married = married;
	}

	eat() {
		// ...
	}
}

let person = new Person("Gosho", 16);
person.eat();

// Access modifiers
// Note: all properties and methods are public by default, no need to use the word "public"
class BankAccount {
	private ID: number;
	
	protected deposit(money: number) {
		// ...
	}
}

// You can create properties via the constructor
class Person1 {
	constructor(public name: string, public age: number, public married?: boolean) {
		// You can access the name, age and married properties, because by adding an
		// access modifier in the constructor creates them
		this.name = name;
		this.age = age;
		this.married = married;
	}
}

let person1 = new Person1("Gosho", 16, false);
console.log(person1.name + " " + person1.age + " " + person1.married);

class Person2 {
	constructor(public name: string, public age: number, public married?: boolean) {
		// In this case, and in Person1 class, you don't even need to assign the values, 
		// they are automatically assigned by the constructor
	}
}

let person2 = new Person2("Gosho", 16, false);
console.log(person2.name + " " + person2.age + " " + person2.married);


// Getters and setters can be made to be just simple functions
class Person3 {
	constructor(public name: string, private age: number, public married?: boolean) {
	}

	getAge() {
		return this.age;
	}

	setAge(value: number) {
		// And while we're at it, here is an example of simple data validation
		if (value < 0 || value > 140)
			throw new Error("Age must be between 0 and 140");

		this.age = value;
	}
}

let person3 = new Person3("Gosho", 16, false);
person3.setAge(17);
console.log(person3.getAge());

// Or you can specifically implement them
class Person4 {
	constructor(public name: string, private age: number, public married?: boolean) {
	}

	get Age() {
		return this.age;
	}

	set Age(value: number) {
		// And while we're at it, here is an example of simple data validation
		if (value < 0 || value > 140)
			throw new Error("Age must be between 0 and 140");

		this.age = value;
	}
}

var person4 = new Person4("Gosho", 16, false);
person4.Age = 16;
console.log(person4.Age);

// IMPORTANT NOTE ON CONVENTIONS
// it's a convention to use cammelCase for almost everything, including properties
// so, private values are given an underscore in the beginning of the name

class Person5 {
	constructor(public name: string, private _age: number, public married?: boolean) {
	}

	// We can now use the word "age" with lowercase letters for the setter and getter
	// before it was causing issues with the variable being also named "age", so we had
	// to make the setter and getter "Age", which isn't a good convention
	get age() {
		return this._age;
	}

	set age(value: number) {
		// And while we're at it, here is an example of simple data validation
		if (value < 0 || value > 140)
			throw new Error("Age must be between 0 and 140");

		this._age = value;
	}
}

var person5 = new Person5("Gosho", 16, false);
person5.age = 16;
console.log(person5.age);

/***********/
/* Modules */
/***********/

// Unless configured otherwise, everything in a TypeScript file is public to everything else in that file (scope)
// What if we want to have something be accessable from other files?
// Things that we can acccess from other files are called modules.
// Note: examples are of two different files, that's why they are all commented

// Let's say we want to put the class Person into another file, called person.ts

/* Inside person.ts:
 *
 * // We need the word "export" to signify that it can be accessed from the outside world
 * export class Person {
 * 		constructor(public name: string, public age: number, public married?: boolean) {
 * 		}
 * }
 *
 */

/* Inside program.ts
 *
 * // To get stuff from the outside world, you use "import"
 * // in the curly brackets you specify what you want to get
 * // and after that, in the quotes, you specify where you want to get it from (the path)
 * // Note: as you can see, we have './person' and not './person.ts', because 'person' is the name of the module, while 'person.ts' is the name of the file
 * import { Person } from './person';
 *
 * let myPerson = new Person("Gosho", 16, false);
 */