Functions

Function ek naam wala, dobara istemal ho sakne wala code ka block hai. Jahan bhi aap khud ko milta julta code ek se zyada martaba likhte hue paao, aksar yeh ishara hota hai ke use function bana dena chahiye.

function greet(name) {
  return `Hello, ${name}!`;
}

console.log(greet("Alice"));
console.log(greet("Bob"));

Hello, Alice!
Hello, Bob!

• function ek function declaration shuru karta hai, uske baad uska naam aur parentheses mein parameters aate hain
• return ek value wapas bhejta hai jahan se function call hua tha — iske baghair, function undefined wapas karta hai
• name ek parameter hai — ek placeholder jo function call karte waqt jo bhi pass karo usse bhar jaata hai

Default parameters

Aap ek parameter ko default value de sakte hain, jisse woh optional ban jaata hai — call karne wale use bilkul chhor bhi sakte hain, ya jab kuch alag chahiye to override kar sakte hain.

function greet(name, greeting = "Hello") {
  return `${greeting}, ${name}!`;
}

console.log(greet("Alice"));
console.log(greet("Bob", "Hi"));

Hello, Alice!
Hi, Bob!

Aage: arrow functions — functions likhne ka ek mukhtasar syntax.