advance-types.js

// INTERSECTION TYPES

interface Admin {
  name: string;
  privileges: string[];
}

interface Employee {
  name: string;
  startDate: Date;
}

type ElevatedEmployee = Admin & Employee;

const e1: ElevatedEmployee = {
  name: 'jose',
  privileges: ['create-server'],
  startDate: new Date()
}

type Combinable = string | number;
type Numeric = number | boolean

type Universal = Combinable & Numeric;

// TYPES GUARDS

function add(a: Combinable, b: Combinable) {
  if (typeof a === 'string' || typeof b === 'string') {
    return a.toString() + b.toString();
  }
  return a + b;
}

type UnknownEmployee = Employee | Admin;

function printEmployeeInformation(emp: UnknownEmployee) {
  console.log('name = ', emp.name);
  if ('privileges' in emp) {
    console.log('privilege = ', emp.privileges);
  }
  if ('startDate' in emp) {
    console.log('start date = ', emp.startDate);
  }
}

printEmployeeInformation(e1);

class Car {
  drive(){console.log('driving')}
}

class Truck {
  drive(){console.log('driving a truck')}
  loadCargo(amount: number){console.log(`loading cargo ${amount}`)}
}

type Vehicle = Car | Truck;

const v1 = new Car()
const v2 = new Truck()

function useVehicle(vehicle: Vehicle) {
  vehicle.drive();
  if (vehicle instanceof Truck) {
    vehicle.loadCargo(1000)
  }
}

useVehicle(v1);
useVehicle(v2);

// DISCRIMINATED UNOINS

interface Bird {
  type: 'bird';
  flyingSpeed: number;
}

interface Horse {
  type: 'horse';
  runningSpeed: number;
}

type Animal = Bird | Horse;

function moveAnimal(animal: Animal) {
  let speed;
  switch (animal.type) {
    case 'bird':
      speed = animal.flyingSpeed;
      break
    case 'horse':
      speed = animal.runningSpeed;
  }
  console.log('moving with speed: ', speed);
}

moveAnimal({type: 'bird', flyingSpeed: 100});

// TYPE CASTING

const paragraph = <HTMLInputElement>document.querySelector('#text')!;
const paragraph2 = document.querySelector('#text')! as HTMLInputElement;

paragraph.value = 'hi there';

// INDEX PROPERTIES

interface ErrorContainer {
  [keyName: string]: string;
}

const errorBag: ErrorContainer = {
  'email': 'not a valid number',
  'user-name': 'user name is required'
}

// FUNCTION OVERLOADS
function addOverload(a: number, b: number): number;
function addOverload(a: string, b:string): string;
function addOverload(a: Combinable, b: Combinable) {
  if (typeof a === 'string' || typeof b === 'string') {
    return a.toString() + b.toString();
  }
  return a + b;
}

const add1 = addOverload(1,3);
const add2 = addOverload('jose', 'lombana');

// OPTIONAL CHAINING

const fetchUserData = {
  id: 'u1',
  name: 'jose david',
  job: {
    title: 'developer',
    description: 'frontend dev - backend'
  }
}

console.log(fetchUserData?.job?.title);

// NULLISH COHALESCING

const userInput = null;

const storedData = userInput ?? 'default'; // print default when is null or undefined