🚀 Advanced JavaScript

👉 This is where most interview questions come from

🧠 1. ES6+ Features (Modern JavaScript)

🔹 Arrow Functions
const add = (a, b) => a + b;

🔹 Destructuring
const user = { name: "Sid", age: 26 };
const { name, age } = user;

🔹 Spread Operator
let arr = [1,2,3];
let newArr = [...arr, 4];

👉 Makes code clean readable

🔄 2. Array Methods (Very Important 🔥)

🔹 map()

👉 Transform data
let nums = [1,2,3];
let result = nums.map(n => n * 2);

🔹 filter()

👉 Filter data
let nums = [1,2,3,4];
let even = nums.filter(n => n % 2 === 0);

🔹 reduce()

👉 Aggregate data
let nums = [1,2,3];
let sum = nums.reduce((acc, curr) => acc + curr, 0);

🌐 3. Fetch API (Connect to Backend)

fetch("https://api.example.com/data")
.then(res => res.json())
.then(data => console.log(data));

👉 Used to get data from APIs

🔥 4. Promises (Core Concept)

👉 Handle async operations

let promise = new Promise((resolve, reject) => {
resolve("Success");
});

States:
• Pending
• Resolved
• Rejected

⚡ 5. Async / Await (Modern Way)

async function getData() {
let res = await fetch("url");
let data = await res.json();
console.log(data);
}

👉 Cleaner than .then()

🔁 6. Event Loop

👉 JavaScript is single-threaded

• Call Stack
• Callback Queue
• Event Loop

👉 Ensures async code runs smoothly

🎯 Mini Project

👉 Create:
• Fetch API data (like users)
• Display on webpage

💡 Pro Tips

> Focus on:
• Promises
• Async/Await
• Fetch API

> Practice real APIs (JSONPlaceholder)

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