자바스크립트의 변수 - var
ES6 - let, const
undefined
값을 가짐var a
console.log(a) //undefined
var a = 10
console.log(a) //10
let a
console.log(a) // undefined
let a = 10 // 'a' has already been declared ~
let b = 10
console.log(b) //10
b = 100
console.log(b) //100
const a
console.log(a) // Missing initializer in const declaration
const b=10
console.log(b) //10
const b=2 // Identifier 'b' has already been declared (at
const c=10
console.log(c) //10
c=100
console.log(c) //Assignment to constant variable.
각 특징을 알고 적확하게 변수 선언을 하는 습관을 들이는게 좋을 것 같다.