Functions

Ek function ke parameters aur return value dono ko type kiya ja sakta hai. TypeScript har call site ko in types ke against check karta hai, isliye ghalat kism ka argument pass karna foran pakra jaata hai, function ke chalne par nahi.

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

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

Hello, Alice!
Hello, Bob!

void, aur optional/default parameters

void ek aise function ko mark karta hai jo koi maani khez value wapas nahi karta. Ek parameter jiske baad ? ho woh optional hota hai — call karne wale usko chhor sakte hain — aur ek parameter ka default value bhi ho sakta hai, jo usko ek alag tareeqe se optional bana deta hai: chhorne par woh khud ba khud fill ho jaata hai.

function logScore(name: string, score: number = 0): void {
  console.log(`${name}: ${score}`);
}

logScore("Alice", 95);
logScore("Bob");

Alice: 95
Bob: 0

Aage: arrow functions — ek chhota syntax, same typing rules ke sath.