Make Async Await Work In Promises
10 Jul 2017 - Help improve this postI have some issues with getting async and await working inside of Promise’s.
When using this code:
function returnSomething(name) {
return new Promise((resolve, reject) => {
const somethingElse = await returnSomethingElse();
return resolve(somethingElse);
});
}
I got this error
/app/app.js:63
const something = await returnSomethingElse();
^^^^^^^^^^^^^^^^^^^
SyntaxError: Unexpected identifier
I knew I needed to add async into the mix, so I was changing the function to
async function returnSomething(name) { // <--- this line
return new Promise((resolve, reject) => {
const somethingElse = await returnSomethingElse();
return resolve(somethingElse);
});
}
But still no luck, then I realised I didn’t have an async function. The arrow function in the new Promise is not async! So I change the code to this and it worked:
function returnSomething(name) {
return new Promise(async (resolve, reject) => { // <--- this line
const somethingElse = await returnSomethingElse();
return resolve(somethingElse);
});
}
But now we have a function with a Promise inside of it which is async. That seems like a bit much, don’t you think?
Let’s clean this up a bit. Because the function is already async it means it’s behaving like a Promise. No need for new Promise inside of the function.
async function returnSomething(name) {
const somethingElse = await returnSomethingElse();
return somethingElse;
}
If returnSomethingElse rejects, we will catch the error in the parent function of returnSomething:
(async () => {
try {
const something = await returnSomething();
console.log(something);
} catch (e) {
console.error(e);
}
})();
Happy coding! – Found a mistake or a typo? Please submit a PR to my GitHub-repo.