Snippets fro a fast typescript course

typescript-fast-course.ts

// you will learn
// error compilations types

console.log("hello world");

// Types
// string
let myString:string;
myString = "Hello" + "World";
myString = myString.slice(0,3);

// number
let myNum: number;
myNum = 22;

// boolean
let myBool: boolean;
myBool = false;

//any
let myVar: any;
myVar = false;

// arrays
let StringArray: string[];
StringArray = ['Hello', 'World'];

const numArray:number[] = [1, 2, 3];
const boolArray: boolean[] = [true, false, false];

// Tuple - an array with defined elements
let strNumTuple: [string, number];
strNumTuple = ['Hello', 7];
strNumTuple = ['Hello', 7, 1, 3];

// void
let myVoid: void = undefined;
let myNull: null = null;
let myundefined: undefined = undefined;

// Functions

function getSum(num1: number, num2:number):number {
    return num1 + num2;
}

console.log(getSum(1, 4));

let myConcatenation = function(num1:string, num2:string):string{
    return num1 + num2;
}

let mySum = function(num1: number|string, num2: number|string):number {
    if(typeof num1 == 'string'){
        num1 = parseInt(num1);
    }
    if(typeof num2 == 'string') {
        num2 = parseInt(num2);
    }

    return num1 + num2;
}

// optional parameter
function getName(firstName:string, lastName?:string):string {
    if(lastName == undefined) {
        return firstName;
    }
    return `${firstName} ${lastName}`;
}


// void function
function myVoidFunction():void {
    return;
}

/**
 * Interfaces
 */ 

function showTodo(todo: {title: string, text: string}):void{
    console.log(`${todo.title} ${todo.text}`);
}

// definition interface
interface iTodo {
    title: string;
    text:string
}

let myTodo:iTodo = {title: 'Eat Dinner', text: 'just remenber to eat'};

function todoFunction(todo: iTodo):void {
    console.log(todo);
}


/**
 * Classes - properties + methods
 * modifiers - to access to props and methods
 */
interface IUser {
    name: string;
    email: string;
    age: number;
    register();
    showmeAge();
    ageinYears();
    payInvoice();
}

class User implements IUser {
    // you can add private, public, protected
    name: string;
    public email: string;
    protected age: number;

    constructor(
        name: string,
        email:string,
        age: number
    ) {
        this.name = name;
        this.email = email;
        this.age = age;

        console.log(`user ${this.name}`)
    }

    public register() {
        console.log(`${this.name} is now registered`)
    }

    public showmeAge() {
        return this.age;
    }

    private AgeinYears() {
        return this.age + ' years';
    }

    payInvoice() {
        console.log(`${this.name} is now registered`);
    }
}

// inheritance
class Member extends User {
    id: number;
    
    constructor(id:number, name:string, email: string, age:number){
        super(name, email, age);
        this.id = id;
    }

    payInvoice() {
        super.payInvoice();
    }

}

let john = new User('Joe MacMillan', '[email protected]', 45);
let gordon = new Member('Gordon', 'Clark', '[email protected]', 40);


const result = mySum('2','2');
console.log(result);