1. What is the difference between var, let, and const?

• var → Function scoped, redeclare ও reassign করা যায় (পুরোনো JS)
• let → Block scoped, redeclare করা যায় না কিন্তু reassign করা যায়
• const → Block scoped, redeclare বা reassign কোনোটাই করা যায় না

var a = 10;
var a = 20; 
let b = 30;
b = 40; 
const c = 50;

---

2. What is the difference between map(), forEach(), and filter()?

• forEach() → শুধু loop চালায়, কিছু return করে না
• map() → প্রতিটা element নিয়ে নতুন array return করে
• filter() → condition অনুযায়ী নতুন array বানায়

const numbers = [1, 2, 3, 4, 5];
numbers.forEach(n => console.log(n));
const squares = numbers.map(n => n * n); 
console.log(squares); 
const evens = numbers.filter(n => n % 2 === 0);
console.log(evens); 

---

3. What are arrow functions in ES6?

Arrow functions provide a shorter and cleaner syntax for writing functions.
They also bind this lexically, meaning they inherit this from the surrounding scope.

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

Benefits:

• Shorter syntax
• Lexical this binding
• Suitable for callbacks and functional programming

---

4. How does destructuring assignment work in ES6?

Destructuring allows extracting values from arrays or objects directly into variables.

const numbers = [10, 20, 30];
const [x, y, z] = numbers;
console.log(x, y, z); 
const user = { name: "Amdad", age: 19 };
const { name, age } = user;
console.log(name, age); 

---

5. Explain template literals in ES6. How are they different from string concatenation?

Template literals are defined using backticks (`).
They allow embedding variables and expressions inside a string using ${} and support multi-line strings.

const name = "Bayijid";
const age = 19;
const text1 = "My name is " + name + " and I am " + age + " years old.";
const text2 = `My name is ${name} and I am ${age} years old.`;
console.log(text1);
console.log(text2);