Arrow function,Callback function,use Effect...

An arrow function is a shorter way to write a function in JavaScript.
It uses the => symbol instead of the function keyword.

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Basic Syntax

const add = (a, b) => {
return a + b;
};

You can also write it even shorter if it's just one line:

const add = (a, b) => a + b;

Example:

Instead of writing:

function sayHello() {
  console.log("Hello");
}

You can write:

const sayHello = () => {
  console.log("Hello");
};

Key Points:

• It uses => instead of the function keyword.
• It's shorter and cleaner.
• It automatically uses the this from the place where it was written.

Callback Function:

A callback function in JavaScript is a function that is passed as an argument to another function, and it is called (or "called back") later.

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Example:

function greet(name, callback) {
  console.log("Hello, " + name);
  callback();
}

function sayBye() {
  console.log("Goodbye!");
}

greet("John", sayBye);

Output:

Hello, John
Goodbye!

Here:

• sayBye is a callback passed to greet.
• greet calls sayBye() after greeting.

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In Short:

A callback is:

• A function passed into another function
• Called later (after something happens)
• Useful for things like waiting, repeating, or responding to events

UseEffect:

useEffect is a React Hook that lets you run side effects in function components.

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useEffect runs after your component renders. You use it to do things like fetch data, update the DOM, or set up timers.

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Basic Syntax:

import { useEffect } from 'react';

useEffect(() => {
  // Code to run (side effect)
});

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Important Notes:

• useEffect runs after render.
• You can control when it runs using the dependency array ([]).
• You can return a function to do cleanup (like clearing timers or unsubscribing from listeners).

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