Closure in js

JavaScript variables can belong to:

The local scope or The global scope

Global variables can be made local (private) with closures.

Closures makes it possible for a function to have "private" variables.

Local Variables
A local variable is a "private" variable defined inside a function.

A function can access all variables in the local scope.

Example

a is a local variable defined inside the function:

function myFunction() {
  let a = 4;
  return a * a;
}

Global Variables
A global variable is a "public" variable defined outside a function.

A function can access all variables in the global scope:

Example

a is global variable defined outside the function:

let a = 4;
function myFunction() {
  return a * a;
}

In a web page, global variables belong to the page.

Global variables can be used (or changed) by all scripts in the page.

A local variable can only be used inside the function where it is defined. It is private and hidden from other functions and other scripting code.

Global and local variables with the same name are different variables. Modifying one, does not modify the other.