Hey folks! Today was one of those sessions where the lightbulb 💡 really went off — I finally understood some confusing but fundamental stuff in React and JavaScript. Here's a breakdown of what I learned (and trust me, it's gold 👑 for beginners and even intermediates who missed the tiny details):

⚛️ 1. Why JSX Needs Double Curly Braces for Styling

"Wait, I'm passing a JavaScript object, so why can't I just wrap it directly with {} like that?"

<button {style={backgroundColor: "red"}}>Redbutton> ❌

But now I know:
Because JSX doesn't allow curly braces around attributes like that. In JSX, attributes must be in the format:
attributeName={jsValue}

<button style={{ backgroundColor: "red" }}>Redbutton>

So in incorrect example:

...

You're trying to put JavaScript inside the HTML tag syntax itself, which breaks JSX rules.
JSX expects props (like style) to be written as:

In our case:

Red

This is valid because:

  • style is the prop name
  • { ... } is the JSX way of saying “the value of this prop is a JavaScript expression”
  • And that expression happens to be an object 🔁

🔁 2. Does the Whole Component Re-render on State Change?

I asked:

When I click a button and change color using setColor("pink"), does the whole component re-render? Does React repaint everything?

✅ Answer: Yes, the function re-runs, but React is smart!

  • The entire JSX is re-evaluated
  • But React only updates the actual DOM parts that changed (thanks to Virtual DOM and diffing)

So your UI stays efficient and smooth 🧈✨

👀 3. Why Does console.log() Run Twice in React?

I dropped a console.log("let's see") inside JSX and freaked out when it printed twice 😅

💡 Reason:

React.StrictMode in development intentionally renders components twice (but ONLY in dev mode) to catch bugs.

✅ Production will render just once. No worries! All part of the dev experience.

🧠 4. JS Return Rule: Why Code After return is Ignored

I made this mistake:

return (
  <>
    <h1>Hih1>
  >
);
<App />; // ❌ doesn't work

Lesson learned:
➡️ After return, nothing else inside the function runs.

So if you want to return , include it inside the return (...) block.

📦 5. Do I Have to Use the Same Prop Name?

I was passing state like this:

<App count={count} />

And I wondered: Do I have to call it count in the child?

✅ Nope!

You can rename it however you want when passing:

<App totalClicks={count} />

Just make sure the name matches in the child:

function App({ totalClicks }) {
  return <h2>{totalClicks}h2>;
}

🔄 Arrays/Objects confusion – Built-in or User-Defined?
Absolute 🔥 of a question:

“Why do we call arrays/objects user-defined if we didn’t define how they work?”

Here’s the truth:

Object and Array types are built-in to JavaScript ✅

But when you create a structure with them, like:

const person = { name: "Aman", age: 22 };
const colors = ["red", "green"];

That structure is user-defined — you decide the keys, values, and layout. You didn’t create the engine, but you decided what’s inside it.

🧠 Built-in container, user-defined content.

Primitive types
These are the basic building blocks — they are predefined and immutable (can't be changed directly).

String

Number

Boolean
These are called primitive because:

They hold single values.

They are not objects.

They are copied by value.

So yes, they are predefined by the language.

💡 TL;DR:

Type Predefined User-defined Stored As
Primitive ✅ Yes ❌ No By value
Non-primitive ✅ (base) + ✅ you define shape ✅ Yes By reference

🧩 Topics I Crushed Today:

  • JSX attribute syntax
  • React re-render logic ⚛️
  • StrictMode behavior 👀
  • JavaScript return rules 🧠
  • Prop naming and passing 📨

If you're learning React — bookmark this, share it, and remember:

Even your "smallest doubts" are super valid — clear them early and loud! 🙌

Let me know if you want this as a tweet thread, blog intro, or carousel — we can style it however you like! 🎨