typescript 선택적 변수

 

const name = "kim",
    age = 21,
    gender = "male";

const sayHi = (name, age, gender) => {
    console.log(`hello ${name}, your are ${age}, you are a ${gender}`);
}

sayHi(name, age, gender);

export {};

 

결과 : hello kim, your are 21, you are a male

 

const name = "kim",
    age = 21,
    gender = "male";

const sayHi = (name, age, gender) => {
    console.log(`hello ${name}, your are ${age}, you are a ${gender}`);
}

sayHi(name, age);

export {};

 

javascript 결과 :

hello kim, your are 21, you are a undefined

 

typescript 결과 :

5 const sayHi = (name, age, gender) => {
                                ~~~~~~
    An argument for 'gender' was not provided.

 

const name = "kim",
    age = 21,
    gender = "male";

const sayHi = (name, age, gender?) => {
    console.log(`hello ${name}, your are ${age}, you are a ${gender}`);
}

sayHi(name, age, gender);

export {};

 

매개변수에 ? 를 붙여주면 선택적 변수로 변하기 때문에

컴파일이 된다.

 

결과 : hello kim, your are 21, you are a undefined