Get async value from firestore

Question

I am struggling with async operations. I am trying to simply get a value from firestore and storing it in a var.

I manage to receive the value, I can even save it in

Answer 1

You have things the wrong way around. It's much easier than you think it is.

function getValues(collectionName, docName) {
    return db.collection(collectionName).doc(docName).get().then(function (doc) {
        if (doc.exists) return doc.data().text;
        return Promise.reject("No such document");
    }};
}

If a function returns a promise (like db.collection(...).doc(...).get()), return that promise. This is the "outer" return above.

In the promise handler (inside the .then() callback), return a value to indicate success, or a rejected promise to indicate an error. This is the "inner" return above. Instead of returning a rejected promise, you can also throw an error if you want to.

Now you have a promise-returning function. You can use it with .then() and .catch():

getValues('configuration','helpMessage')
    .then(function (text) { console.log(text); })
    .catch(function (err) { console.log("ERROR:" err); });

or await it inside an async function in a try/catch block, if you like that better:

async function doSomething() {
    try {
        let text = await getValues('configuration','helpMessage');
        console.log(text);
    } catch {
        console.log("ERROR:" err);
    }
}

---

If you want to use async/await with your getValues() function, you can:

async function getValues(collectionName, docName) {
    let doc = await db.collection(collectionName).doc(docName).get();
    if (doc.exists) return doc.data().text;
    throw new Error("No such document");
}