How Closure makes handling Data leaks, state management, and messy code too simple — Master Advanced Javascript

Vamsi Krishna Kodimela
Angular Simplified
Published in
3 min readMar 31, 2024


Data leaks, poor state management, and messy and hard-to-maintain code are always problems when we work with front-end applications, and almost every one of us is a victim.

Well, no more! Javascript Closures is our one-stop solution for crafting well-organized and secured Javascript Applications.


Closures are a powerful concept that allows us to create functions that remember and access variables from their outer scope even after the outer function has returned. This “remembering” creates a private space for data, promoting encapsulation and state management.

Think of it this way: Imagine a function like a box. Inside the box, there might be smaller compartments holding valuable data. When the function finishes its main task, the box might be thrown away (the function returns). However, the smaller compartments (closures) are hidden within the box and can still be accessed.

Why Closures..?

  • Data Protection: Variables declared within a closure are inaccessible from the outside world, preventing accidental modification and promoting data integrity.
  • State Management: Closures allow you to create private state variables within functions, enabling stateful behavior without relying on global variables.
  • Modular Code: Functions with closures become self-contained units, improving code organization and reusability.

Closures in Action

Now that we understand the core idea of closures. Let’s see how they can be used in real time for data encapsulation and state management.

  • Simple Counter Function
function createCounter() {
let count = 0; // Private variable due to closure
return {
increment() {
getCount() {
return count;

const counter1 = createCounter();
console.log(counter1.getCount()); // Output: 2

// Trying to access count directly won't work (encapsulation)
// console.log(count); // ReferenceError: count is not defined
  • Private Data in Modules (TypeScript)
// module.ts
export function createModule(data: string) {
let internalData = data; // Private due to closure

return {
getData() {
return internalData;
setData(newData: string) {
internalData = newData;
// main.ts
import { createModule } from './module';

const myModule = createModule("Initial data");
console.log(myModule.getData()); // Output: "Initial data"

// We cannot access internalData directly (encapsulation)
// console.log(internalData); // Error: internalData is not defined

myModule.setData("Updated data");
console.log(myModule.getData()); // Output: "Updated data"


Closures are not just a fancy JavaScript feature but a powerful tool for building secure, maintainable, and well-organized applications. So, the next time you encounter data privacy concerns or state management challenges, consider wielding the power of closures to conquer them with elegance!

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