Async - Await

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Async and await are 2 keywords in JS (not only, as they are present also in other languages like C#) which changed the game with callbacks etc.

In reality, async function is wrapping the function into the Promise (read about Promises above).

When async function returns the value it really makes resolve(returnedValue) and when the async function throws an error it really makes reject(error).

What it really means? Consider 2 way of doing some stuff.

function resultWithPromise () {
return new Promise((resolve, reject) => {
  resolve('Result');
});

}

async function resultWithAsync () {
  return 'Result';
}

async function checkIt() {
  console.log(await resultWithAsync()); // -> Result
  console.log(await resultWithPromise()); // -> Result

  resultWithPromise().then(result => console.log(result)); // -> Result
  resultWithAsync().then(result => console.log(result)); // -> Result
}

As you can see above - as the result of async returning the promise and await resolving the promise, you can await on Promise and do .then on async function.

Generally it is considered that using async and await makes code much cleaner because you are not nesting with .then and .catch.

One last thing about .catch. Using await funcReturningPromise may throw an error if promise will be rejected, so to prevent runtime errors you can wrap it in try catch (e) .