React useState and useEffect

A.Esakki Muthu — Thu, 01 Oct 2026 12:27:55 +0000

useState Definition

useState is a React Hook used to store and manage changing data in a component.

Purpose

We use useState when a value can change and we want React to update the UI when that value changes.

Example
const [count, setCount] = useState(0);

Here:

count → current value
setCount → changes the value
0 → initial value

If we click a button:

setCount(count + 1);

The value changes:

0 → 1 → 2 → 3

And React updates the screen.

Where can we use it?

useState is commonly used for:

Counter
Input fields
ON/OFF buttons
Show/Hide
Login status
Shopping cart
Search text
Easy memory

useState = Store changing data + update the UI

useEffect Definition

useEffect is a React Hook used to run some code after a component renders or when a particular value changes.

Purpose

We use useEffect when we need to perform an action based on rendering or changes in data.

For example:

Fetch data from an API
Start a timer
Change the browser title
Listen for events
Work with external systems
Example
useEffect(() => {
console.log("Component rendered");
}, []);

The code inside useEffect runs after the component renders.

What is []?
useEffect(() => {
console.log("Hello");
}, []);

The empty [] means the effect runs after the initial render.

If we use:

useEffect(() => {
console.log("Count changed");
}, [count]);

The effect runs when count changes.

useState → "What data should I store?"

useEffect → "What code should I run after rendering or when something changes?"

Advice...

A.Esakki Muthu — Thu, 24 Sep 2026 10:54:32 +0000

Still current AI era Companies hiring Java Full stack developers ? Asked by 2026 Passout Fresher...

Advice

A.Esakki Muthu — Wed, 05 Aug 2026 18:46:17 +0000

Hi guys, I'm a 2026 fresher. I'm confused about choosing between Java, Python, .NET, and MERN. Is Full Stack still worth learning with AI growing so fast? Can a skilled fresher still get a job? Any advice?

Hi guys, I'm a 2026 passout fresher. I'm currently learning Full Stack Development, but I'm really confused. With AI growing so fast, is Full Stack still a good career choice, or will its demand decrease? I'm also confused about which backend technology to

A.Esakki Muthu — Wed, 05 Aug 2026 18:43:28 +0000

DEV Community: A.Esakki Muthu

React useState and useEffect

Advice...

Advice

Hi guys, I'm a 2026 passout fresher. I'm currently learning Full Stack Development, but I'm really confused. With AI growing so fast, is Full Stack still a good career choice, or will its demand decrease? I'm also confused about which backend technology to