We have discussed before that let and const both are hoisted too. But if you try to access a let or const data structure before it's initialized, this is what you get:

console.log(a);
let a=10;

This error is encountered because a is in temporal dead zone

Temporal Dead Zone

When we declare and initialize data using let and const keywords, unlike var, they are stored in a separate memory space which is not a part of the global space.

So, even though in the first phase of memory allocation, they are hoisted and given value undefined until initialized, they cannot be accessed.

This space between first line of code to execution of code where they are initialized is called the temporal dead zone.

let can be declared in one line and initialized later, but const keyword when used, must be initialized in the same line or throws an error. It is more strict than let.

⭐ var vs let vs const by freecodecamp
⭐ js introduction by interviewbit