Returning multiple values

As we've discussed in the The Promise constructor chapter, just like normal functions, a Promise can have a single return value. But oftentimes you'll want to return multiple things.

Fortunately, JavaScript supports the object and the array destructuring operators that makes it easy to use a single variable to hold multiple things.

For example, a Promise can resolve with an array of values:

const getValues = () => new Promise((res) => {
  const user = "user";
  const group = "group";
  res([user, group]);
});

const [user, group] = await getValues();
// user, group

Or an object with known fields:

const getValues = () => new Promise((res) => {
  const user = "user";
  const group = "group";
  res({user, group});
});

const {user, group} = await getValues();
// user, group

Of course, it's the same pattern that you'd use for synchronous functions:

const getValues = () => {
  const user = "user";
  const group = "group";
  return {user, group};
};

const {user, group} = getValues();
// user, group

And works the same with async functions too:

const getValues = async () => {
  const user = "user";
  const group = "group";
  return {user, group};
};

const {user, group} = await getValues();
// user, group