1. String concatenation
console.log('my' + ' cat');
console.log('1' + 2);
console.log(string literals: 1 + 2 = ${1 + 2});
2. Numeric operators
console.log (2 + 1); // 더하기
console.log (2 - 1); // 빼기
console.log (2 / 1); // 나누기
console.log (2 * 1); // 곱하기
console.log (2 ** 1); // 제곱
3. Increment and decrement operators
let counter = 2;
const preIncrement = ++counter;
console.log(preIncrement: ${preIncrement}, counter: ${counter});
=> preIncrement: 3, counter: 3 출력
counter = counter + 1;
preIncrement = counter;
const postIncrement = counter++;
console.log(postIncrement: ${postIncrement}, counter: ${counter});
=> preIncrement: 3, counter: 4 출력
postIncrement = counter;
counter = counter + 1;
const preDecrement = --counter;
console.log(preDecrement: ${preDecrement}, counter: ${counter});
const postDecrement = counter--;
console.log(postDecrement: ${postDecrement}, counter: ${counter});
=> preIncrement: 3, counter: 3 출력
=> preIncrement: 3, counter: 2 출력
4. Assignment operators
let x = 3;
let y = 6;
x += y; // x = x + y
x -= y;
x *= y;
x /= y;
5. Conparison operators
console.log(10 < 5);
console.log(10 <= 5);
console.log(10 > 5);
console.log(10 <= 5);
6. Logical operators
|| (or)
가장 첫 번째 true 값을 찾음
const value1 = false;
const value2 = 4 < 2;
function check() {
for (let i = 0; i < 10; i++) {
// wasting time
console.log('omg')
};
return true;
};
console.log(
or: ${value1 || value2 || check()});
&& (and)
가장 첫 번째 false 값을 찾음
console.log(
and: ${value1 && value2 && check()});
! (not)
반대의 값을 찾아줌
console.log(!value1);
Note!
가장 복잡한 값을 가장 뒤에 놓는다
7. Eqiality
onst stringFive = '5';
const numberFive = 5;== loose equality, with type conversion
console.log(stringFive == numberFive);
console.log(stringFive != numberFive);=== strict equality, no type conversion
console.log(stringFive === numberFive);
console.log(stringFive !== numberFive);
=> true 출력
=> false 출력
=> false 출력
=> true 출력
object equality by reference
const dongdu1 = { name: dongdu };
const dongdu2 = { name: dongdu };
const dongdu3 = dongdu;
console.log(dongdu1 == dongdu2);
console.log(dongdu1 === dongdu2);
console.log(dongdu1 === dongdu3);
=> false 출력
=> false 출력
=> true 출력
8. Conditional operators
- if
- else if
- else
const name = 'dongdu';
if (name === 'dongdu') {
console.log('Welcome, dongdu');
} else if (name === 'coder') {
console.log('You are amazing coder');
} else {
console.log('unknown');
};
9. Ternary operator
condition ? value1 : value2;
console.log(name === 'dongdu' ? 'yes' : 'no');
10. Switch statement
조건을 다양하게 체크할 때 사용
const browser = "IE";
switch (browser) {
case "IE":
console.log('go away!');
break;
case "Chrome":
case "Firefox":
console.log('I love you!');
break;
default:
console.log('same all!');
break;
};
11. Loops
while
조건문이 맞을 때 실행
let i = 3;
while (i > 0) {
console.log(while: ${i});
i--;
};do while
일단 실행 후 검사
do {
console.log(do while: ${i});
i--;
} while (i > 0);
for loop
for (begin; condition; step)
for (i = 3; i > 0; i--) {
console.log(for: ${i});
};
for (let i = 3; i > 0; i = i - 2) {
console.log(for: ${i});
};
nasted loops
for (let i = 0; i < 10; i++) {
for (let j = 0; j < 10; j++) {
console.log(i: ${i}, j: ${j});
};
};
break
아예 루프를 끝내는 것
continue
현재만 스킵, 다음 스탭으로 넘어감
