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Asynchronous Programming

async/await

Synchronous-Looking Async Code
💡 async/await, EK, "SUBTITLE, TRACK" hai, Promise, ke, ANDAR — YE, ASYNCHRONOUS, CODE, ko, SYNCHRONOUS, CODE, jaisa, DIKHATA, hai, PADHNE, mein, JABKI, INTERNALLY, WOH, ABHI, BHI, ASYNC, HI, hai.

async, KEYWORD, EK, FUNCTION, ko, MARK, karta hai, JO, HAMESHA, EK, Promise, RETURN, karta hai. await, KEYWORD, (SIRF, async, FUNCTIONS, ke, ANDAR, VALID), EK, Promise, ke, RESOLVE, hone, tak, EXECUTION, ko, "PAUSE" karta hai, BINA, MAIN, THREAD, ko, BLOCK, kiye.

try-catch, BLOCKS, USE, karके, ERRORS, HANDLE, kiye, jaate, hain (Promise.catch() ki, JAGAH) — YE, SYNCHRONOUS, ERROR, HANDLING, ki, TARAH, feel, hota hai, JO, READ, karne, mein, EASIER, hai.

async function getUserWithPosts(userId) {
  try {
    const user = await fetchUser(userId);
    const posts = await fetchPosts(user.id);
    return { ...user, posts };
  } catch (err) {
    console.error("Failed:", err.message);
    throw err;
  }
}

// Parallel execution, jab, DEPENDENCY, nahi, hai:
async function getBothUsers() {
  const [user1, user2] = await Promise.all([fetchUser(1), fetchUser(2)]);
  return { user1, user2 };
}
⏱️
async/await, EK, "SUBTITLE, TRACK" hai, Promise, ke, ANDAR — YE, ASYNCHRONOUS, CODE, ko, SYNCHRONOUS, CODE, jaisa, DIKHATA, hai, PADHNE, mein, JABKI, INTERNALLY, WOH, ABHI, BHI, ASYNC, HI, hai.
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⚡ Quick Recap
  • async function, HAMESHA, Promise, RETURN, karta hai
  • await, execution, ko, PAUSE, karta hai, bina, main, thread, BLOCK, kiye
  • try-catch, se, errors, HANDLE, hote, hain — synchronous, error, handling, jaisa, FEEL, hota hai
On this page (2 subtopics)

Modern, Node.js, (ES, Modules, ke, saath), TOP-LEVEL, await, SUPPORT, karta hai — async, FUNCTION, ke, ANDAR, WRAP, kiye, BINA, MODULE, ke, TOP, LEVEL, PAR, DIRECTLY, await, USE, kiya, ja, sakta hai.

// ES module (package.json: "type": "module")
const data = await fetch("https://api.example.com/data");
console.log(await data.json());

for await (const item of asyncIterable), ASYNC, ITERABLES, (jaise, STREAMS) ko, LOOP, karne, ka, MODERN, WAY, hai — HAR, ITEM, ke, liye, AUTOMATICALLY, await, karta hai.

💡Tip: Readable streams, Node.js, mein, async, iterable, HOTE, HAIN — for await (const chunk of stream), se, DIRECTLY, ITERATE, kiya, ja, sakta hai, MANUAL, EVENT, LISTENERS, ke, BAJAYE.