Use Ref

 in case of useref no need to deal with vdom directly real dom of browser is updated

Venice

That's a fantastic observation, and you're touching on the core power of useRef. You are absolutely correct that useRef allows you to bypass React's VDOM diffing process for direct DOM manipulation.

However, let's add one layer of precision: useRef itself doesn't update the DOM. It gives you a direct, stable reference to something (usually a DOM node), and you use that reference to update the DOM yourself, completely outside of React's normal render cycle.

Let's contrast the two flows.

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The useState Flow (The "Official" React Way)

This is the "ask for permission" model.

1. Trigger: You call setCount().
2. Render: React schedules a re-render. It calls your component, gets a new React Element tree, and builds a new VDOM.
3. Reconciliation (Diffing): React compares the new VDOM to the old one and figures out what changed.
4. Commit: React tells the browser, "Please update the text inside this <p> tag to '1'." The real DOM is updated.

Key takeaway: React is in full control. You declare what you want the state to be, and React figures out the most efficient way to update the real DOM.

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The useRef Flow (The "Backstage Pass" Model)

This is the "act now, ask for forgiveness later (or never)" model.

1. Setup: You declare const inputRef = useRef(null). This creates a plain object like { current: null } that will persist across renders.
2. Attach: You attach it to your JSX: <input ref={inputRef} />.
3. Mount: After the component renders, React does its magic. It finds the actual <input> element in the real DOM and puts a reference to it in your ref object: { current: [the actual HTMLInputElement] }.
4. Manipulation (Your Part): Later, in an event handler, you do this:
   javascript

   const focusInput = () => {
     // You are now directly touching the browser's API.
     // React has NO IDEA this is happening.
     inputEl.current.focus();
   };

   You are not telling React to change the state. You are grabbing the real DOM node and calling a native browser method on it.

Key takeaway: You are in control. You are stepping outside of React's VDOM system and interacting directly with the browser's DOM.

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The Critical Difference: Synchronicity

This is where the distinction becomes vital.

• useState is Asynchronous: When you call setState, the change doesn't happen right away. React batches updates and applies them later during its render cycle. The state variable doesn't change until the next render.

• useRef is Synchronous: When you update ref.current, the change happens immediately. The .current property is just a mutable property on a plain object. There is no re-render, no diffing, no delay. The change is instant.

Why is this so powerful?

Because sometimes you need to do something that isn't related to rendering the UI.

• Focusing an input: This doesn't change the "state" of your app, it's just a browser command.
• Starting/stopping a timer (setInterval/clearInterval): You need to store the timer ID somewhere, but storing it in useState would cause a re-render every time you set it. A ref is perfect for this.
• Integrating with a non-React library: A third-party charting library might give you a method like myChart.updateData(). You need a reference to the DOM element where the chart lives, and you call that method directly.

Summary Table

Feature	useState	useRef
Purpose	Store data that, when changed, should update the UI.	Store data that persists but should not update the UI.
Triggers Re-render?	Yes, always.	No, never.
Update Mechanism	Asynchronous (scheduled by React).	Synchronous (instant).
DOM Interaction	Indirect. You change state, React updates the DOM via its VDOM diffing.	Direct. You get a reference to the real DOM node and call its methods yourself.
Analogy	Filling out a form and giving it to a clerk who processes it.	Having a key to the back office and going in yourself.

So, to circle back to your statement: Yes, useRef lets you deal directly with the real DOM, which is precisely why it's used for cases where you want to sidestep the VDOM's diffing and rendering process.

yes use state is asynchronous and it is processed in batch by react and it is applied while rendering but if u pass functional update in setter function of state instead of updating the state through setter function then ?

Excellent question 👏 this is where React understanding becomes advanced level.

You’re asking:

If useState is asynchronous and batched…
what happens when we pass a functional update to the setter?

Let’s break this properly.

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🔁 Normal State Update (Problem Case)

setCount(count + 1);
setCount(count + 1);

You might expect +2.

But React batches updates.

Both lines read the same old value of count.

Example:

If count = 0:

• First call → setCount(0 + 1)

• Second call → setCount(0 + 1)

After batching → result = 1 (not 2)

Because both updates used stale value.

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⚡ Functional Update Version

setCount(prev => prev + 1);
setCount(prev => prev + 1);

Now what happens?

React stores these updater functions in a queue.

During rendering, React executes them in order:

1. prev = 0 → returns 1

2. prev = 1 → returns 2

Final state = 2 ✅

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🔥 Why Functional Update Works

Because you're not using the stale closure variable (count).

You're telling React:

"When you're ready to update, use the latest value you have at that moment."

So even though state updates are:

• ✅ Asynchronous

• ✅ Batched

• ✅ Processed during render

Functional updates always receive the latest computed state.

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🧠 Important Clarification

You said:

instead of updating the state through setter function

⚠️ Small correction:

Even in functional update, you are still using the setter function.

You're just passing a function instead of a value.

Both are valid:

setCount(5);              // Direct value
setCount(prev => prev+1); // Functional update

The difference is how React calculates the next state.

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🏗 What React Actually Does Internally

React keeps a queue of state updates for each hook.

When batching happens:

• It doesn't immediately update state

• It stores updates in a queue

• During render, it processes them sequentially

If update is:

• Value → replace state

• Function → call function with latest state

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🕒 Is Functional Update Still Asynchronous?

YES.

It is still:

• Batched

• Scheduled

• Applied during render

It is NOT synchronous like useRef.

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🧪 Example to See Difference

const handleClick = () => {
  setCount(count + 1);
  setCount(count + 1);
  console.log(count);
};

Output:

• count remains old value in console

• final state = +1

Now:

const handleClick = () => {
  setCount(prev => prev + 1);
  setCount(prev => prev + 1);
};

Final state = +2 ✅

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🎯 Golden Rule

Use functional update when:

• New state depends on previous state

• Multiple updates in same function

• Inside setTimeout / async code

• Inside event listeners

• Inside loops

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🏆 Final Mental Model

Update Type	Uses Latest State?	Safe in Batching?
setCount(count + 1)	❌ No (closure value)	❌ Risky
setCount(prev => prev + 1)	✅ Yes	✅ Safe

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You are now touching React's internal state queue mechanism.