boolean
console.log(2 === 2)
console.log(2 !== 2)
console.log('abc' === 'abc')
console.log(true && true)
console.log(true && false)
console.log(false && true)
console.log(false && false)
console.log(true || true)
console.log(true || false)
console.log(false || true)
console.log(false || false)
console.log(!true)
console.log(!false)
typeof 연산자
console.log(typeof 101)
console.log(typeof 'abc')
console.log(typeof true)
console.log(typeof 5)
console.log(typeof 5.02)
console.log(typeof '5')
console.log(typeof "5")
console.log(typeof `5`)
let name = 'abc'
function sayHello() {
console.log('Hello')
}
console.log(typeof name)
console.log(typeof sayHello)
console.log(typeof 'abc' + 'def')
console.log(typeof 3 - 2)
console.log(typeof ('abc' + 'def'))
console.log(typeof (3 - 2))
형 변환(Type Conversion)
console.log('10' + '5')
console.log(10 + 5)
console.log(Number('10') + Number('5'))
console.log(String(10) + String(5))
let x = 345
console.log(x)
console.log(String(x))
console.log(typeof x)
console.log(typeof String(x))
let y = true
console.log(y)
console.log(String(y))
console.log(typeof y)
console.log(typeof String(y))
let a = '123'
console.log(a)
console.log(Number(a))
console.log(typeof a)
console.log(typeof Number(a))
let b = true
console.log(b)
console.log(Number(b))
console.log(typeof b)
console.log(typeof Number(b))
let c = false
console.log(c)
console.log(Number(c))
console.log(typeof c)
console.log(typeof Number(c))
console.log('------------')
let d = '문자'
console.log(d)
console.log(Boolean(d))
console.log(typeof d)
console.log(typeof Boolean(d))
let e = ''
console.log(e)
console.log(Boolean(e))
console.log(typeof e)
console.log(typeof Boolean(e))
let f = 234
console.log(f)
console.log(Boolean(f))
console.log(typeof f)
console.log(typeof Boolean(f))
let g = 0
console.log(g)
console.log(Boolean(g))
console.log(typeof g)
console.log(typeof Boolean(g))
let h = NaN
console.log(h)
console.log(Boolean(h))
console.log(typeof h)
console.log(typeof Boolean(h))
자동 형 변환
console.log(4 + '3')
console.log(4 + 3)
console.log(4 - true)
console.log(4 * false)
console.log(4 / '2')
console.log('4' ** true)
console.log(4 % 'two')
console.log(3 < '4')
console.log(3 > true)
console.log('3' <= false)
console.log('two' >= 1)
console.log(1 === '1')
console.log(1 === true)
console.log(1 == '1')
console.log(1 == true)
템플릿 문자열(template strings)
let year = 2021
let month = 7
let day = 3
console.log('이 글을 작성한 날은 ' + year + '년 ' + month + '월 ' + day + '일 입니다.')
console.log(`이 글을 작성한 날은 ${year}년 ${month}월 ${day}일 입니다.`)
let myNumber = 5
function getTwice(x) {
return x * 2
}
console.log(`${myNumber}의 두 배는 ${getTwice(myNumber)}입니다.`)
null과 undefined
let myVar
console.log(myVar)
myVar = null
console.log(myVar)
console.log(null == undefined)
console.log(null === undefined)