Type annotations

타입스크립트에서 매개변수와 반환값이 어떤 type인지 설정하는 코드입니다.

Type inference

타입스크립트는 함수의 반환값 타입을 확인합니다.

Function

const add = (num1: number, num2: number): number => {
  return num1 + num2;
};

const subtract = (num1: number, num2: number): number => {
  return num1 - num2;
};

function divide(num1: number, num2: number): number {
  return num1 / num2;
}

function multiple(num1: number, num2: number): number {
  return num1 * num2;
}

const logger = (message: string): void => {
  console.log(message);
};

const throwError = (message: string): void => {
  if (message) throw new Error(message);
};
/*
const throwError = (message: string): never => {
  throw new Error(message);
};
 */

const todayForecast = {
  date: new Date(),
  weather: 'sunny',
};

const logWeather = ({
  date,
  weather,
}: {
  date: Date;
  weather: string;
}): void => {
  console.log(date, weather);
};

logWeather(todayForecast);

Object

const profile = {
  name: 'jinsu',
  age: 26,
  coords: {
    lat: 0,
    lng: 15,
  },
  setAge(age: number): void {
    this.age = age;
  },
};

const { age, name }: { age: number; name: string } = profile;
// const { age }: number = profile; errrrrror

const {
  coords: { lat, lng },
}: { coords: { lat: number; lng: number } } = profile;

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