Promises
Promise, EK, OBJECT, hai, JO, EK, ASYNCHRONOUS, OPERATION, ke, EVENTUAL, COMPLETION, (YA, FAILURE) ko, REPRESENT, karta hai — THREE, STATES, HOTI, HAIN, pending, fulfilled, aur, rejected.
.then(), SUCCESS, HANDLE, karta hai, .catch(), ERROR, HANDLE, karta hai, aur, .finally(), HAR, HAAL, mein, RUN, hota hai. Promise.all(), MULTIPLE, PROMISES, ko, PARALLEL, mein, RUN, karके, SAB, ke, RESOLVE, hone, ka, WAIT, karta hai.
function fetchUser(id) {
return new Promise((resolve, reject) => {
setTimeout(() => {
if (id > 0) resolve({ id, name: "Aarav" });
else reject(new Error("Invalid ID"));
}, 1000);
});
}
fetchUser(1)
.then((user) => console.log("User:", user))
.catch((err) => console.error("Error:", err.message));
Promise.all([fetchUser(1), fetchUser(2)])
.then((users) => console.log("Both users:", users));- Promise = async operation ke, eventual, completion/failure, ko, represent, karta hai
- States: pending, fulfilled, rejected
- Promise.all() = multiple promises, PARALLEL, mein, RUN, karके, SAB, ka, WAIT, karta hai
.then() calls, CHAIN, kiye, ja, sakte, hain — HAR, .then(), EK, NAYA, Promise, RETURN, karta hai, JISME, PREVIOUS, .then() ka, RETURN, VALUE, PASS, hota hai — SEQUENTIAL, ASYNC, STEPS, ke, liye, USEFUL, hai.
fetchUser(1)
.then(user => fetchPosts(user.id))
.then(posts => console.log("Posts:", posts))
.catch(err => console.error(err));Promise.race(), JO, BHI, PROMISE, SABSE, PEHLE, SETTLE, (resolve YA, reject) hota hai, USका, RESULT, RETURN, karta hai — TIMEOUT, IMPLEMENT, karne, ke, liye, USEFUL, hai. Promise.any(), PEHLE, FULFILLED, (SUCCESS) PROMISE, ka, RESULT, RETURN, karta hai.