data/docs/javascript_promises.txt

JavaScript Promises handle asynchronous operations in a cleaner way than callbacks.

Promise States:
- Pending: initial state, operation not complete.
- Fulfilled: operation completed successfully.
- Rejected: operation failed.

Creating a Promise:
const myPromise = new Promise((resolve, reject) => {
  if (success) resolve(result);
  else reject(error);
});

Consuming a Promise:
myPromise
  .then(result => console.log(result))
  .catch(error => console.error(error))
  .finally(() => console.log('always runs'));

async/await syntax (ES2017) is syntactic sugar over promises:
async function fetchData() {
  try {
    const data = await fetch(url);
    const json = await data.json();
    return json;
  } catch (error) {
    console.error(error);
  }
}

Promise utility methods:
- Promise.all([p1, p2]): runs in parallel, resolves when all resolve.
- Promise.race([p1, p2]): resolves/rejects with first settled promise.
- Promise.allSettled(): waits for all, returns all results regardless of success/failure.