Hoisting

Hoisting is when a variable or function declaration gets moved to the top of its scope before the code runs. It means you can use a variable or function before you create (declare) it.

console.log(hoistedVariable); // undefined

var hoistedVariable = "initialized var hoistedVariable";

console.log(hoistedVariable); // correct value

In the example above, I used the variable "hoistedVariable" in the first console.log before creating it. Often, this would cause an error, but due to hoisting, it will show "undefined." The computer will move the variable creation var hoistedVariable to the top, but won't move the variable value. When I assign the value to the variable, the second console.log will show the correct answer.

The "let" and "const" keywords don't work well with hoisting. Even though they're moved to the top of their scope, they don't get a value right away. It creates a "temporal dead zone" where you can't access the variables until they're declared (created). If you try to use "let" or "const" variables before declaring them, you'll get a "ReferenceError."