What are closures in JavaScript?

If you are looking What are closures in JavaScript? the answer is here.
Closures are an important concept related to how functions work with lexical scoping. Here’s a breakdown:

Definition:
A closure is the combination of a function bundled together (enclosed) with references to its surrounding state (the lexical environment). In simpler terms, it allows a function to remember and access its lexical scope even when that function is executed outside that scope.

Key Points:

1. Lexical Scope: Functions in JavaScript create closures based on their lexical scope, which means they remember where they were defined, not where they are executed.
2. Access to Outer Function Scope: Inner functions declared inside another function (parent function) have access to variables and parameters of their parent function even after the parent function has finished executing.

Example:

function outerFunction() {     
      let outerVar = "I'm outside!";
     function innerFunction() {         
          console.log(outerVar); // innerFunction has access to outerVar     
      }     
      return innerFunction;
 }
 let closureExample = outerFunction();
 closureExample(); // Outputs: I'm outside!

Explanation:

• outerFunction defines outerVar and innerFunction.
• innerFunction is returned from outerFunction and assigned to closureExample.
• When closureExample is called later, it still has access to outerVar due to the closure created during the execution of outerFunction.

Use Cases:

• Closures are often used for data encapsulation, creating private variables and functions.
• They are also useful for implementing function factories or currying in functional programming.

Understanding closures is crucial for mastering JavaScript’s functional programming capabilities and ensuring efficient and secure code design.