hw0k

function sound(animal: Dog | Cat) {
  if (animal instanceof Dog) {
    // animal은 Dog로 추론됨.
    animal.bark();
    animal.meow(); // error TS2339: Property 'meow' does not exist on type 'Dog'.
    return;
  }
  if (animal instanceof Cat) {
    // animal은 Cat으로 추론됨.
    animal.bark(); // error TS2339: Property 'bark' does not exist on type 'Cat'.

hw0k

class Dog {
  bark = () => {
    console.log('bark!');
  };
}

class Cat {
  meow = () => {
    console.log('meow!');
  };

hw0k

interface Window {
  title: string;
}

interface Window {
  ts: import("typescript");
}

declare function getWindow(): Window;

hw0k

type TBase = {
  t: number;
};

interface IBase {
  i: number;
}

// extends 사용
interface I1 extends TBase {}

hw0k

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

const henry: Human = {
  name: '남현욱',
  age: 20,
};

hw0k

function checkNumberIsZero(par: number): boolean {
  return par === 0;
}

checkNumberIsZero(0); // true
checkNumberIsZero([]); // Error!
checkNumberIsZero(""); // Error!
checkNumberIsZero(false); // Error!
checkNumberIsZero(this); // Error!

hw0k

// Problem 1
const obj = { width: 10, height: 15 };

const area = obj.width * obj.heigh; // NaN

// Problem 2
function checkNumberIsZero(par) {
  return par == 0;
}

hw0k

function pipe(...functions) {
  return input => functions.reduce((value, func) => func(value), input);
}

function multiplyTwice(x) {
  return x * 2;
}

function addFive(x) {
  return x + 5;

hw0k

function pipe(...functions) {
  return input => functions.reduce((value, func) => func(value), input);
}

function compose(...functions) {
  return input => functions.reduceRight((value, func) => func(value), input);
}

hw0k

function createPage({
  title = '', // 해당 값이 없을 때 기본으로 사용할 값
  body = '',
  tags = [],
  actions = [],
} = {}) { /* ... */ }

// usage
createPage({
  title: 'Hello world!',