Closures in JavaScript

The concept of closures in JavaScript allows functions to remember and access variables from their lexical scope, even when the function is executed outside that scope.

What is a Closure?

• Definition
  • A closure is a function that has access to its own scope, the scope of the outer function, and the global scope.
• Key Characteristic
  • The inner function retains access to the variables and parameters of the outer function even after the outer function has returned.

How Closures Work

1. Creating a Closure:
2. A closure is created every time a function is created.

3. The inner function retains access to the variables and scope of the outer function.

4. Lexical Scoping:

5. Lexical scoping means that a function's scope is defined by its physical position in the code.

6. The closure has access to variables in three scopes:

   • Local scope (variables defined between its curly brackets)
   • Outer function's scope
   • Global scope

7. Variables Retention:

8. The inner function retains the variables of the outer function even after the outer function has finished executing.
9. This retained scope is what makes a closure.

Example

function outerFunction() {
    let outerVariable = 'I am from the outer function!';

    function innerFunction() {
        // Inner function accessing the outer function's variable
        console.log(outerVariable);
    }

    return innerFunction;
}

const myClosure = outerFunction(); // outerFunction has returned, but the closure is alive
myClosure(); // Outputs: I am from the outer function!