TypeScript ka Introduction

TypeScript, JavaScript ka ek superset hai — har valid JavaScript program pehle se hi valid TypeScript hota hai. TypeScript jo upar se add karta hai woh ek type system hai: aap apne data ka shape describe kar sakte ho (strings, numbers, objects, functions), aur compiler check karta hai ki aapka code un shapes ko actually respect karta hai, isse pehle ki woh run ho.

TypeScript code directly run nahi hota — yeh pehle plain JavaScript mein compile hota hai. Type annotations sirf isliye hote hain taaki code likhte waqt mistakes pakdi ja sakein; ek baar compile hone ke baad, output ek normal JavaScript hota hai jisme type information hata di gayi hoti hai, aur wahi actually execute hota hai.

Types ki zaroorat kyun hai?

Code run karne se pehle hi bugs pakadna — property name mein typo, ya galat kism ki value pass karna, turant ek error ke roop mein dikh jaata hai, runtime surprise ke bajaye
Behtar editor support — autocomplete, inline documentation, aur safe renaming, sab is baat par depend karte hain ki editor ko pata ho ki ek value kis type ki hai
Khud ba khud documented code — ek function ki type signature aapko batati hai ki woh kya expect karta hai aur kya return karta hai, uski implementation padhe bina
Zyada safe refactoring — ek type ka shape change karte hi, woh har jagah flag ho jaati hai jahan purane shape ko assume kiya gaya tha

Ek jaldi sa preview

Yeh raha real TypeScript ka ek program, jo is page ke apne compiler par actually run hua hai — koi mockup nahi:

main.ts

Khud try karo →

let greeting: string = "Hello from TypeScript!";
console.log(greeting);

Output

Hello from TypeScript!

Bas itna hi — ek normal variable, bas ek explicit type ke sath. Agla lesson aapka pehla poora program run karta hai aur exactly samjhaata hai ki kya ho raha hai.

Aapka Pehla TypeScript Program →