What is the temporal dead zone?

Question

I\'ve heard that accessing let and const values before they are initialized can cause a ReferenceError because of something called the

Answer 1

In case of let and const variables, Basically, Temporal Dead Zone is a zone

"before your variable is declared",

i.e where you can not access the value of these variables, it will throw an error.

ex.

let sum = a + 5;        //---------
//some other code       //         | ------>  this is TDZ for variable a
                        //         |
console.log(sum)        //---------
let a = 5;

above code gives an error

the same code will not give an error when we use var for variable 'a',

ex.

var sum = a;                            
console.log(sum)     //prints undefined
var a = 5;