interface는 js에는 존재하지 않음. 즉 컴파일 타임에만 필요함

optional property

• ?

interface Person1 {
    name: string;
    age: number;
}

interface Person2 {
    name: string;
    age?: number;  
}
function hello1(person: Person1): void {
    console.log(`안녕하세요! ${person.name} 입니다.`)
}
function hello2(person: Person2): void {
    console.log(`안녕하세요! ${person.name} 입니다.`)
}

hello1({name: "Mark"}); //error
hello2({name: "Anna"}); //okay
//? 사용시 있어도 되고, 없어도 됨

• index
  추가적인 프로퍼티

interface Person3 {
    name: string;
    age?: number;
    [index: string]: any;
}

const p32: Person3 = {
    name: "Anna",
    systers: ["Sung", "Chan"]
}

fuction in interface

interface Person4 {
    name: string;
    age?: number;
    hello(): void;
}

const p51: Person4 = {
    name: 'Mark',
    age: 30,
    hello: function(): void{
        console.log(`안녕하세요! ${this.name} 입니다.`)
    },
}
const p52: Person4 = {
    name: 'Mark',
    age: 30,
    hello(): void{
        console.log(`안녕하세요! ${this.name} 입니다.`)
    },
}

class in interface

interface IPerson1 {
    name: string;
    age?: number;
    hello(): void;
}

//interface를 이용해서 class를 만듬 (implements)
class Person implements IPerson1 {
    name: string;
    age?: number | undefined;

    constructor(name: string) {
        this.name = name;
    }

    hello(): void {
        console.log(`안녕하세요! ${this.name} 입니다.`)
    }

}

const person = new Person('Mark');
person.hello();

interface extends interface

interface IPerson2 {
    name: string;
    age?: number;
}

interface IKorean extends IPerson2 {
    city: string;
}

const k: IKorean = {
    name: 'hun',
    city: 'seoul',
};

function interface

interface HelloPerson {
    (name: string, age?: number): void;
}

const helloPerson: HelloPerson = function(name: string) {
    console.log(`안녕하세요 ${name} 입니다. `)
}

readonly

수정 불가능한 값

type alias vs interface

//function
// type alias
type EatType = (food: string) => void;
// interface
interface IEat {
  (food: string): void;
}

--------------------------------------------------
//Array
// type alias
type PersonList = string[];
// interface
interface IPersonList {
  [index: number]: string;
}

--------------------------------------------------
//intersection
interface ErrorHandling {
    success: boolean;
    error?: { message: string };
}
interface ArtistsData {
    artists: { name: string }[];
}

// type alias
type ArtistsResponseType = ArtistsData & ErrorHandling;

// interface
interface IArtistsResponse extends ArtistsData, ErrorHandling {}
let art: ArtistsResponseType;
let iar: IArtistsResponse;

--------------------------------------------------
//union types
interface Bird {
    fly(): void;
    layEggs(): void;
}
interface Fish {
    swim(): void;
    layEggs(): void;
}
type PetType = Bird | Fish;
//interface IPet extends PetType {}// error
//class Pet implements PetType {} // error 

--------------------------------------------------
// deckaration merging - interface
interface MergingInterface {
    a: string;
}
interface MergingInterface {
    b: string;
}

let mi: MergingInterface;
//mi.a mi.b 가능 (합쳐짐)
//alias는 불가