What are Promises and async/await?

Promises represent the eventual completion or failure of an asynchronous operation.

Promise States:
- Pending - initial state
- Fulfilled - operation completed successfully
- Rejected - operation failed

Creating Promises:

const promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("Success!");
  }, 1000);
});

Using Promises:

promise
  .then(result => console.log(result))
  .catch(error => console.error(error))
  .finally(() => console.log("Done"));

Async/Await (ES2017):

async function fetchData() {
  try {
    const result = await promise;
    console.log(result);
  } catch (error) {
    console.error(error);
  }
}

Benefits:
- Cleaner than callbacks
- Better error handling
- Avoids callback hell
- More readable asynchronous code