operator

Operator

String Concatenation

console.log('my' + ' name'); // my name
console.log('20' + 22); // 2022
console.log(`string literals: 20 + 22 = ${20 + 22}`); // string literals: 20 + 22 = 2022

Numeric operators

console.log(1+1); // 2 add
console.log(1-1); // 0 substract
console.log(1/1); // 1 divide
console.log(1*1); // 1 multiply
console.log(6%4); // 1 remainder
console.log(3**2); // 9 exponentiation

Increment and decrement operators

let number = 0
const preincrement = ++number
// number = number + 1
// increment = number

const postincrement = number++
// postincrement = number
// number = number + 1

let counter = 1
const predecrement = --counter
const postdecrement = counter--

Assignment operators

let x = 2
let y = 5
x += y // x= x+y
x -= y
x *= y
x /= y

Comparison operators

console.log( 1 < 9 ) // less than
console.log( 1 <= 9 ) // less than or equal
console.log( 1 > 9 ) // greater than
console.log( 1 >= 9 ) // greater than or equal

Logical operators

• or, and

const v1 = false;
const v2 = 4 < 2;

console.log(`or: ${ v1 || v2 || check() }`)
console.log(`and: ${ v1 && v2 && check() }`)

function check() {
	for(let i = 0; i < 10; i++) {
    	console.log('hello')
    }
    return true;
}

// true가 출력
// or 연산시 간단한 연산부터 앞에 놓는 것이 좋음

Equality

• == loose equality, with type conversion
• === strict equality, no type conversion

Conditional operators: if

• if, else if, else

const age = 30;
if ( age === 30 ) {
	console.log('welcome, 30!')
} else if (age === 20) {
	console.log('hello 20!')
} else {
	console.log('unknown')
}

// welcome, 30!

Ternary operator: ?

• condition ? value1 : value2

console.log(age === 30? 'welcome 30' : 'unknown')

Switch Statement

1) use for multiple if checks
2) use for enum-like value check
3) user for mulitple type checks in TS

const browser = 'dfdf';
switch (browser) {
    case 'IE' :
        console.log('go away!');
        break;
    case 'Chrome' :
    case 'Firefox' : // chrome과 파이어폭스는 내용이 같기 때문에 붙여서 출력이 가능
        console.log('love you!');
        break;
    default :
        console.log('same all!');
        break;
}

break, continue

1) iterate from 0 to 10 anf print only even numbers(use continue)

    for (let i = 0; i < 11; i++) {
        if (i % 2 !== 0) {
            continue;
        } console.log(`q1. ${i}`);
    }

2) iterate from 0 to 10 and print numbers until reaching 8 (use break)

    for (let i = 0; i < 11; i++ ) {
        if (i > 8) {
            break;
        }
        console.log(`q2. ${i}`);
    } 

loops

let num = 3;
while (num > 0) {
	console.log(`while: ${num}`)
    num--;
}

do {
	console.log(`do while: ${num}`)
} while (num > 0)