1. 변수형 문제

let a = 1
let b = 2 
console.log(a,b)
let temp = a
a = b 
b = temp
console.log(a,b)

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2) 자료형 문제
* 20 + 30 -> 50
* “20” + “30” ->2030
* “Hello” + " " + 2021 -> Hello 2021
* 1 + 2 * 3 -> 7
* (1 + 3) ** 2 ->16
* 1 / 0 -> 무한
* 6 % 2 -> 0
* 7.5 % 2 -> 1.5
* 5 == 5 -> True
* 5 === 5 -> True
* 5 == “5” -> False
* 5 === “5” -> False
* 5 != 5.0 -> False
* 5 !== 5.0 -> False
* “true” === True
* 5 <= 5.0 -> True
* 5 >= 5 ->True
* true || true -> True
* true || false -> True
* true && true -> True
* true && false ->False
* !true -> False
* !false -> True