JavaScript Async Reference

const promise = new Promise((resolve, reject) => {
  if (success) resolve(data); # success
  else reject(error); # failure
});

promise
  .then(data => console.log(data)) # handle success
  .catch(err => console.error(err)); # handle error

async function fetchData() {
  try {
    const response = await fetch(url); # wait for promise
    const data = await response.json(); # parse JSON
    return data;
  } catch (error) {
    console.error(error); # handle error
  }
}

# GET request
fetch("https://api.example.com/data")
  .then(res => res.json())
  .then(data => console.log(data));

# POST request
fetch(url, {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify(data)
});

Promise.all([promise1, promise2]) # wait for all
  .then([res1, res2] => { });

Promise.race([promise1, promise2]) # first to finish
  .then(result => { });

Promise.allSettled([p1, p2]) # all results
Promise.any([p1, p2]) # first success

# Promise chain
promise
  .then(data => { })
  .catch(err => { }) # catch errors
  .finally(() => { }); # always runs

# Async/await
try {
  await asyncFunction();
} catch (e) {
  console.error(e);
}