Hoisting is where a variable and function declaration is moved to the top of its scope during compilation. This means that variables and functions can be used before they are declared in the code. You should know that since the declaration is hoisted but not the initialization of the variable the variable will be undefined. A function will be hoisted differently and will be available.

Here are some quick examples.

Variable Hoisting

console.log(aVariable); // undefined, not ReferenceError

var aVariable = 5;

console.log(aVariable); // 5

In this example:

– At first `console.log` prints `undefined` because the declaration of `aVariable` has been hoisted but int initialized.

– The second `console.log` prints `5` because `aVariable` has been initialized.

Example of Function Hoisting

console.log(helloWorld()); // Outputs: "Hello, World!"

function helloWorld() {
  return "Hello, World!";
}

In this example:

– The call to `helloWorld()` works even though it appears before the function declaration in the code because the entire function declaration has been hoisted.