1. Operator 기본정리
// 1. String concatention
console.log('my' + 'cat'); // (문자열과 문자열을 더할 수 있다
console.log('1' + 2); //문자열에 숫자를 더하면 숫자가 문자열로 변환
console.log(`string literals: 1 + 2 = ${1 + 2}`); //``기호 사용하면 변수값을 사용가능
console.log("ellie`s \n\tbook");
//2. Numeric Operators
console.log(1 + 1); //add
console.log(1 - 1); //substract
console.log(1 / 1); //divide
console.log(1 * 1); //multiply
console.log(5 % 2) //remainder
console.log(2 ** 3); //exponentiation(2의 3승)
//3. Increment and decrement operators
let counter = 2;
const preIncrement = ++counter;
//counter = counter + 1;
//preIncrement = counter;
console.log(`preIncrement : ${preIncrement}, counter: ${counter}`);
const postIncrement = counter++;
//postIncrement = counter;
// counter = counter + 1;
console.log(`postIncrement : ${postIncrement}, counter : ${counter}`);
//4. Assignment operatorts
let x = 3;
let y = 6;
console.log(x += y) ; // x = x + y;
console.log(x -= y) ; // x = x - y;
console.log(x *= y) ; // x = x * y;
console.log(x /= y) ; // x = x / y;
// 5 greter than, less than
console.log(10 > 6);
//6 Logical operators 중요하다 : || (or), &&(and), !(not)
const value1 = false;
const value2 = 4 < 2;
// ||(or) true가 하나만 있으면 true , *진짜 중요한 point : or 연산자느 처음으로 ture가 나오면 거기서 멈춤*
console.log(`or : ${value1 || value2 || check()}`);
function check(){
for(let i = 0 ; i < 10; i ++){
//wasting time
console.log('1');
}
return true;
}
// &&(and) 모두 true 여야지 true , 그리고 heavy한 거는 항상 맨뒤 ex) 함수등등
// 그리거 null check 확인할 떄 많이 씀
console.log(`and : ${value1 && value2 && check()}`);
function check(){
for(let i = 0 ; i < 10; i ++){
//wasting time
console.log('1');
}
return true;
}
//7. Equality
const stringFive = '5';
const numberFive = 5;
// == loose equality, 타입을 변경해서 검사
console.log(stringFive == numberFive);
console.log(stringFive != numberFive);
// === strict equality 타입이 다르면 달라!
console.log(stringFive === numberFive);
console.log(stringFive !== numberFive);
// object eqality by reference
const ellie1 = { name : 'ellie'};
const ellie2 = { name : 'ellie'};
const ellie3 = ellie1;
console.log(ellie1 == ellie2);
console.log(ellie1 === ellie2);
console.log(ellie1 === ellie3 );
// eqiality - puzzler
console.log( 0 == false);
console.log(0 === false);
console.log('' == false);
console.log('' === false);
console.log(null == undefined);
console.log(null === undefined);
//8 if, else if, else
const name = 'aiden';
if(name === 'aiden') {
console.log("welcome, aiden");
}else if (name === 'coder'){
console.log("sleep");
}else{
console.log("whooo!!!");
}
// 9. Ternary oerator : ?
// condition ? value1 : value2;
console.log(name === 'aiden' ? 'yes' : 'no');
//10 switch
const browser = 'IE';
switch(browser) {
case 'IE': console.log('집가자'); break;
case 'firefox': console.log('fox집가자'); break;
case 'chrome': console.log('chrome집가자'); break;
default : console.log('def집가자'); break;
}
// 11. Loops
let i = 3;
while(i > 0) {
console.log(`while : ${i}` );
i--;
}
//12 do,while
do {
console.log(`do while : ${i}`);
i--;
} while(i > 0);
//13 for
for(i = 3 ; i > 0; i--){
console.log(`for : ${i}`);
}
for(let i = 3; i > 0; i = i -2) {
//inline variable declaration
console.log(`lnline variable for : ${i}`);
}
// nested loops
for(let i = 0 ; i < 10 ; i++){
for(let j = 0; j < 10; j++) {
console.log(`i : ${i}, j : ${j}`);
}
}
//break, continue
//Q1. iterate form 0 to 10 and print only even numbers(use continue);
for(i = 0; i <= 10; i++) {
if(i % 2 == 1 ) {
continue;
}else{
console.log(i);
}
}
//Q2. iterate form 0 to 10 and print numbers until reaching 8 (use break);
for(i = 0; i <= 10; i++){
if(i <=8 ){
console.log(i);
}else{
break;
}
}
JavaScript
복사
