var, let, const 차이점

Remark : javascript 문법이 느슨한 것을 보충한 것이 let, contst 이다.

1.var 변수를 중복 선언해도 에러가 없다.


var name = 'seoul'
console.log(name) // seoul

var name = 'busan'
console.log(name) // busan

var name = 'seoul'

console.log(name) // seoul

var name = 'busan'

console.log(name) // busan

2.let 변수를 중복 선언해도 에러가 난다.


let name = 'seoul'
console.log(name) // seoul

let name = 'busan'
console.log(name) // Uncaught SyntaxError: Identifier 'name' has already been declared

let name = 'seoul'

console.log(name) // seoul

let name = 'busan'

console.log(name) // Uncaught SyntaxError: Identifier 'name' has already been declared

3.const 는 변수값 수정불가


const name = 'seoul'
console.log(name) // seoul

const name = 'busan'
console.log(name) // Uncaught SyntaxError: Identifier 'name' has already been declared
// 변수값 수정 불가
name = 'kimhea'
console.log(name)     //Uncaught TypeError: Assignment to constant variable.

const name = 'seoul'

console.log(name) // seoul

const name = 'busan'

console.log(name) // Uncaught SyntaxError: Identifier 'name' has already been declared

// 변수값 수정 불가

name = 'kimhea'

console.log(name) //Uncaught TypeError: Assignment to constant variable.