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 galat kism ka argument pass karna turant pakda jaata hai, function ke run hone 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 meaningful value return nahi karta. Ek parameter jiske baad ? ho woh optional hota hai — callers usko chhod sakte hain — aur ek parameter ka default value bhi ho sakta hai, jo usko ek alag tarike se optional bana deta hai: chhode jaane par woh automatically 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.