What is hoisting?

Answer out loud or in your head first, then compare.

Answer

Hoisting means declarations are processed before the code runs.

JavaScript

console.log(x);

var x = 10;

logs:

undefined

You can think of it as:

JavaScript

var x;

console.log(x);

x = 10;

With let and const:

JavaScript

console.log(x);

let x = 10;

you get a ReferenceError.

Before their declaration, let and const variables are in the Temporal Dead Zone.

A function declaration is hoisted too:

JavaScript

hello();

function hello() {
  console.log("Hello");
}

this works.

How did it go? Be honest — “Not yet” puts the question on your review list.