Javascript let hoisting to the scope or creating where it is?

Question

x declared after fn function but returns its value. Why fn didn't return undefined?

function doWork(){

  let fn = function(){ return x; }
  let x = 2;

  return fn();

}

console.log(doWork()); // 2

Please read how scope works in js https://www.w3schools.com/js/js_scope.asp — asosnovsky, Dec 19 '17 at 19:54
`let` creates variables in a scope. There’s no ordering within a scope, just a "temporal dead zone". If this didn't work, it would be super annoying. — Ry-, Dec 19 '17 at 19:56
https://stackoverflow.com/questions/37916940/why-was-the-name-let-chosen-for-block-scoped-variable-declarations-in-javascri — Zakaria Acharki, Dec 19 '17 at 19:56

score 1 · Accepted Answer · answered Dec 19 '17 at 19:56

Inside of your doWork() function, first you set up a function and assign it to fn -- This function is not invoked yet. You then define x as 2. After this definition you invoke fn() by calling return fn().

Because JavaScript works from top-to-bottom, x is defined at the time you reference fn(), so fn() is able to return x correctly.

This can be seen in the following:

function doWork() {
  let fn = function() {
    return x;
  }
  let x = 2;
  return fn();
}

console.log(doWork()); // 2

Javascript let hoisting to the scope or creating where it is?

1 Answers1