3회차

Truty & Falsy

// False : undefine, null , "" , 0, 0.0,NaN

// True : 그외

let a = "";

if (a) {

console.log("True");

} else {

console.log("False");

}

const getName = (person) => {

if (!person) {

return "객체가 아닙니다"

}

};

let person = { name: "김수현" };

const name = getName(person);

console.log(name);

삼항연산자

// 삼항 연산자

let a = 3;

if (a>0){

console.log("양수")

}

else{

console.log("음수")

}

a>0 ? console.log('양수') : console.log("음수");

let b = [];

if (b.length===0){

console.log("빈배열")

} else {

console.log("안빈배열")

}

(b.length===0)?(console.log("빈배열")):(console.log("안빈배열"));

const arraystste = (b.length===0)?("빈배열"):("안빈배열")

console.log(arraystste)

중첩 삼항 연산자

let score = 40;

(score>90)?(console.log("A+")):((score>50)?(console.log("B+")):(console.log("F")))

()?():() 이렇게쓰고 삼항연산자 사용하기

 

 

단락회로 연산자

const getName = (person)=> {

const name = person && person.name;

return name || "객체가 아닙니다.";

}

let person={name:"뮻"};

const name = getName(person);

console.log(name);

조건문 업그레이드

const isKoreanFood = (food) => {

// if (food==="불고기" || food ==="비빔밥" || food==="떡볶이") {

// return true;

// }

// else{

// return false;

// }

if (["떢볶이","비빔밥","불고기"].includes(food)){

return true;

}

return false;

}

const food1 = isKoreanFood("불고기");

const food2 = isKoreanFood("파스타");

console.log(food1)

console.log(food2)

 

const meal = {

한식 : "불고기",

중식 : "멘보샷",

일식 : "초밥",

양식 : "파스타",

인도식 : "카레"

}

const getMeal = (mealType) =>{

return meal[mealType] || "굶기";

}

console.log(getMeal("중식"))

비구조화 할당

let [one,two,three,four=-1] = ["one","two","three"];

console.log(one,two,three,four);

let a = 10;

let b = 20;

[a,b] = [b,a];

console.log(a,b)

let object = {one:"one",two:"two",three:"three"};

let {one:my_one,two:my_two,three:my_three} = object;

console.log(my_one,my_two,my_three)

spread

const cookie = {

base : "cookie",

madeIn:"korea"

}

const chocochipCookie = {

...cookie,

toping : "chocochip",

}

const blueberryCookie = {

...cookie,

toping:"blueberry"

}

const strawberryCookie = {

...cookie,

toping:"strawberry"

}

console.log(blueberryCookie)

 

비동기

function taskA(a, b, callback) {

setTimeout(() => {

const res = a + b;

callback(res);

}, 3000);

}

function taskB(a, callback) {

setTimeout(() => {

const res = a * 2;

callback(res);

}, 2000);

}

function taskC(a, callback) {

setTimeout(() => {

const res = a * -1;

callback(res);

}, 1000);

}

taskA(4, 5, (a_res) => {

console.log("A Task Result : ", a_res);

taskB(a_res, (b_res) => {

console.log("B RESULT : ", b_res);

taskC(b_res, (c_res) => {

console.log("C_result : ", c_res);

});

});

});

console.log("코드끝");

function taskA(a,b,callback) {

setTimeout(()=>{

const res = a+b;

callback(res);

},3000);

}

taskA(3,4,(res)=>{

console.log("A Task Result : ",res);

});

console.log("코드끝")

 

function isPositive(number, resolve, reject) {

setTimeout(() => {

if (typeof number === "number") {

resolve(number >= 0 ? "양수" : "음수");

} else {

reject("주어진 값이 숫자형이 아닙니다.");

}

}, 2000);

}

isPositive(

"asd",

(res) => {

console.log("성공적으로 수행됨 : ", res);

},

(err) => {

console.log("실패 : ", err);

}

);

 

function isPositive(number, resolve, reject) {

setTimeout(() => {

if (typeof number === "number") {

resolve(number >= 0 ? "양수" : "음수");

} else {

reject("주어진 값이 숫자형이 아닙니다.");

}

}, 2000);

}

function isPositiveP(number){

const executor = (resolve,reject) => {

setTimeout(()=>{

if (typeof number === "number") {

resolve(number >= 0 ? "양수" : "음수");

} else {

reject("주어진 값이 숫자형이 아닙니다.");

}

},2000)

}

const asyncTask = new Promise(executor);

return asyncTask;

}

const res = isPositiveP(101);

res.then((res)=>{console.log("작업성공 : ",res)}).catch((err)=>{console.log("작업실패",err)})

 

 

 

function taskA(a, b, ) {

return new Promise((resolve,reject) => {

setTimeout(() => {

const res = a + b;

resolve(res);

}, 3000);})}

function taskB(a) {

return new Promise((resolve,reject)=>{

setTimeout(() => {

const res = a * 2;

resolve(res);

}, 1000);})}

function taskC(a, callback) {

return new Promise((resolve,reject)=>{

setTimeout(()=>{

const res = a*-1;

resolve(res);

},2000)

});}

taskA(5,1).then((a_res)=>{

console.log("A_RESULT:",a_res);

return taskB(a_res);

}).then((b_res)=>{

console.log("B Result : ",b_res)

return taskC(b_res);

}).then((c_res)=>{

console.log("C Result : ",c_res)

})

async & await

 

function delay(ms) {

return new Promise((resolve) => {

setTimeout(() => {

resolve();

}, ms);

});

}

async function hello_async() {

await delay(3000);

return "hello async";

}

async function main() {

const res = hello_async();

console.log(res);

}

main();