Digvijay Bhakuni

Posted on Oct 6

🧠 Understanding State Management in Web Applications

#webdev #javascript #html #programming

From Cookies to Redux — A Complete Beginner’s Guide

🌍 Introduction

When you open your favorite website, add items to a shopping cart, or log into an app — have you ever wondered how the website “remembers” you even when you refresh or come back later?

This “memory” is made possible by something called State Management.

In this post, we’ll break down what state means, why it’s hard to manage on the web, and explore all the ways developers handle it — from simple cookies to advanced frontend libraries like Redux and Context API.

🔄 What Is “State”?

In simple terms, state means the current data or situation of your app at a given moment.

For example:

In a shopping app: items in your cart
In a login system: which user is logged in
In a to-do app: list of your tasks
In a music app: which song is playing and at what time

Whenever something changes (you add a new task, change a setting, or log out), the state of your app changes too.

⚠️ Why State Management Is Needed

The web runs on HTTP, which is a stateless protocol — meaning:

Each request is independent, and the server doesn’t automatically remember what happened before.

If you log into a website, and then open another page, the server doesn’t know it’s still you — unless it’s managing your state somehow.

That’s why web developers use state management techniques: to keep track of users, data, and app behavior across multiple requests, pages, and sessions.

🧩 Types of State in Web Apps

There are generally two main categories of state:

Type	Description	Example
Client-side State	Data stored and managed in the browser	UI theme (dark/light), cart items, input fields
Server-side State	Data stored and managed on the server	Logged-in user info, database records, session data

Let’s go through all the common techniques used for both.

🧠 Part 1: Client-Side State Management

Client-side state is all about what happens in the browser.
It’s fast, doesn’t require a network call, and is great for UI-related information.

1️⃣ JavaScript Variables / In-Memory State

Simplest form — you store values in variables or React state hooks.

let count = 0;
function increase() {
  count++;
  console.log(count);
}

✅ Pros:

Fast and easy
Great for temporary UI interactions

❌ Cons:

Lost on refresh or page reload

Used In: React, Vue, Angular component states.

2️⃣ Browser Storage

a) Local Storage

Stores data permanently in the browser, until manually deleted.

localStorage.setItem("theme", "dark");
let theme = localStorage.getItem("theme");

✅ Persists even after closing the tab or browser
❌ Accessible only by frontend JavaScript (no security layer)

Good for: saving themes, preferences, small data.

b) Session Storage

Similar to local storage, but cleared when the tab closes.

sessionStorage.setItem("cart", JSON.stringify(items));

✅ Isolated to one tab/session
❌ Disappears after closing the tab

Good for: temporary data like in-progress forms or checkout steps.

c) Cookies

Small pieces of data stored in the browser, sent automatically with every HTTP request.

document.cookie = "username=John; expires=Fri, 31 Dec 2025 23:59:59 GMT";

✅ Server can read cookies automatically
✅ Can persist across sessions
❌ Limited storage (~4KB), and needs security precautions

Good for: sessions, authentication tokens, small preferences.

3️⃣ Frontend State Libraries

Modern web apps are interactive and complex.
That’s why frameworks like React, Vue, and Angular introduced state management libraries to handle component-level and app-wide state efficiently.

🌀 React Context API

Used to share state across multiple components without passing props down manually.

const ThemeContext = React.createContext("light");

✅ Easy for small–medium apps
❌ Can become messy for very large applications

⚙️ Redux

A centralized store that holds the entire app state in one place.

store.dispatch({ type: "ADD_TODO", payload: "Buy milk" });

✅ Predictable and debuggable
✅ Works well in large apps
❌ Slightly complex setup

Used In: React, Angular, and even Flutter (through Redux-like libraries).

📦 Zustand, MobX, Pinia (Vue), NgRx (Angular)

Modern alternatives for simpler or more reactive state management.

✅ Less boilerplate
✅ Easier learning curve
❌ Often limited to the ecosystem they’re built for

🖥️ Part 2: Server-Side State Management

Server-side state keeps track of who you are and what you’re doing on the server — essential for authentication, user sessions, and data persistence.

1️⃣ Sessions

When you log in:

Server creates a session object and stores it in memory or a database.
Server gives the browser a Session ID (usually in a cookie).
Each time the browser makes a request, it sends the session ID back.
Server checks the session ID and retrieves your user data.

Example:

Set-Cookie: sessionId=abc123; HttpOnly

✅ Secure (data is stored server-side)
❌ Can consume memory if many users are online

Used In: Express.js, Django, Spring Boot (via session management).

2️⃣ JWT (JSON Web Tokens)

JWTs are stateless tokens that carry user information securely between client and server.

When you log in:

Server creates a token:

   { "user": "john", "role": "admin" }

Server signs it with a secret key and sends it to the client.
Client stores it (in cookies or localStorage).
Each request includes the token in headers:

   Authorization: Bearer <token>

Server verifies the token — no session storage needed.

✅ Fast and scalable
✅ Works well for APIs and mobile apps
❌ Must handle token expiry and security carefully

3️⃣ Database State

All permanent data — user info, settings, orders — lives in a database.
State changes here are the most persistent form (they survive any restart or reload).

🧭 Putting It All Together

Most real-world apps use a mix of all these techniques.