🔹 Promises in JavaScript

📌 What is a Promise?

A Promise is an object that represents the eventual completion or failure of an asynchronous operation and its resulting value. Promises provide a cleaner, more manageable alternative to traditional callback-based asynchronous programming.

✅ Advantages of Promises over Callbacks:

• Avoid callback hell (nested callbacks).

• Better error handling using .catch().

• Support for chaining asynchronous operations using .then().

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📘 Promise States:

A Promise can be in one of three states:

1. Pending – The initial state, neither fulfilled nor rejected.

2. Fulfilled – The operation completed successfully.

3. Rejected – The operation failed.

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🧩 Basic Syntax:

jsCopyEditconst promise = new Promise((resolve, reject) => {
  // async operation
});

• resolve(value) – Called when the async operation succeeds.

• reject(error) – Called when the async operation fails.

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🕒 Example: Promisify setTimeout

🔧 Code to Create a Promisified Timeout Function:

jsCopyEditfunction setTimeoutPromisified(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

💡 Explanation:

• setTimeoutPromisified returns a Promise that resolves after ms milliseconds.

• setTimeout is used internally, but instead of using a callback directly, the resolution is handled via resolve.

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🔔 Using the Promisified Function:

jsCopyEditfunction callback() {
  console.log("3 seconds have passed");
}

setTimeoutPromisified(3000).then(callback);

🧠 Breakdown:

• After 3 seconds, the Promise resolves.

• .then(callback) is called, executing the callback function.

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⚠️ Tips:

• Always handle possible errors using .catch() in real-world applications.

• Promises are chainable, so you can do:

    jsCopyEditsetTimeoutPromisified(1000)
      .then(() => console.log("1 second passed"))
      .then(() => setTimeoutPromisified(2000))
      .then(() => console.log("2 more seconds passed"));