Javascript ES6,ES7,ES8

There are two different codes.

1.

var myName = "nico";
console.log(myName);
// result = nico

2.

console.log(myName);
var myName = "nico";
// result = undefined

first sentence makes sense.
In case of number 2, we expect that we will have an error.
but the result is undefined. why?

because all Variable become “Hoisting”. so what is “Hoisting”?
Below code is same as number 2.

var myName;
console.log(myName);
myName = "nico";
// result = undefined

Hoisting helps to move Variable declaration to top of the code.

That’s why we would better to use let or const instead of var.

if we use ‘let’ instead of ‘var’ code will be like..
and we can find the error result. why?

console.log(myName);
let myName = "nico";
// result = uncaught reference error: myName is not defined

let also have hoisting but let has TDZ(Temporal Dead Zone)
and nobody can access before myName bind with a value

let myName;
console.log(myName);
myName = "nico"; //after this line, we can access myName
// result = uncaught reference error: myName is not defined

code after hoisting will be the same as var’s case.