ts-tutorial.ts

//tsc --init
//generate a TypeScript configuration file named tsconfig.json. 
//This file specifies how TypeScript should compile your project
//tsc
//tsc --watch


//Basic Types.
let id: number = 5
let company: string = 'Wael Assaf'
let isPublished: boolean = true
let x: any = "String"

//Initializing
let age: number
//Then giving value
age = 25



//Arrays
let ids: number[] = [1, 2, 3, 4, 5]
let arr: any[] = [69, true, "Damn", []]



//Tuple
//With a tuple you can specify the types of each of your array's elements.
//Every value should fall in its type's place.
let person: [number, string, boolean] = [12, "Wael", true]


//Tuple Array
let employee: [number, string][]

employee = [
    [1, 'Wael'],
    [2, 'Kamel'],
    [3, 'Sarah'],
]



//Union
let pId: string | number

pId = 22
pId = "PnMtIdChQN"


//ENUMs
//By default: 0 - 1 - 2 - 3 - etc..
enum Direction1 {
    Up = 1,
    Down,
    Left,
    Right
}

enum Direction2 {
    Up = 'Up',
    Down = 'Down',
    Left = 'Left',
    Right = 'Right'
}




//Objects
type User = {
    id: number
    name: string
}

const user: User = {
    id: 1,
    name: "John"
}


//Type Assertion.
let cid: any = 1

//Two ways to type assert
// let customerId = <number>cid
let customerId = cid as number



//Functions

function addNum(x: number, y: number): number {
    return x + y
}

// console.log(addNum(10, 25))


//Void Returns
function log(msg: number | string): void {
    console.log(msg)
}
// log("Wael Good")




//Interfaces.
interface UserInterface {
    readonly id: number
    name: string
    age?: number
}

const emp: UserInterface = {
    id: 1,
    name: "John"
}



//Interfaces with Functions.
interface MathFunc {
    (x: number, y: number): number
}

const add: MathFunc = (x: number, y:number): number => x + y
const sub: MathFunc = (x: number, y:number): number => x - y




interface PersonInterface {
    id: number
    name: string
    register(): string
}
//Classes
class Person implements PersonInterface {
    id: number
    name: string

    constructor(id:number, name: string) {
        this.id = id
        this.name = name
    }

    register() {
        return `${this.name} is now registered.`
    }
}

const wael = new Person(1, "Wael")
const mike = new Person(2, "Mike")

//Subclass
class Employee extends Person {
    position: string
   
    constructor(id:number, name: string, position: string) {
        super(id, name)
        this.position = position
    }
}

const emp1 = new Employee(3, 'Wael', "CEO")
// console.log(emp1.name)
// console.log(emp1.register())




//Generics
//Used to build reusable components.
function getArray<T>(items: T[]): T[] {
    return new Array().concat(items)
}
  
  let numArray = getArray<number>([1, 2, 3, 4])
  let strArray = getArray<string>(['brad', 'John', 'Jill'])
  
//   strArray.push(1) // Throws error