I think let and const will actually be hoisted in their scope

[DanielWLam]

when you declare a variable with var, it will be hoisted and set value as undefined.
I think let and const are so similar but they are passed the default value 'ReferenceError'

[DrkSephy]

@DanielWLam you are correct. let and const declarations are hoisted, however if you try to reference these variables before they are declared, a ReferenceError is thrown (regardless of the hoisting. This is also known as the Temporal Dead Zone.