proper usage of async and await in JS?

Question

import Firebase from './Firebase' import videoManager from './videoManage'; async function getAllDatabaseLocations() { await let ref = Firebase.database().ref("locations") var user_locations = []; ref.on("value", function (snapshot) { snapshot.forEach(function (datas) { const data = datas.val(); vid_manage = new videoManager(data.videourl); vid_ref = vid_manage.getLocationVideoUrl(); vid_ref.getDownloadURL().then(function (url) { videourl = url; }).catch(function (error) { }); let lokation = data.lokation; let videourl = data.videourl; let openinghours = data.openinghours; let links = data.links; let Lokationer = { lokation: lokation, videoUrl: videourl, openingshours: openinghours, links: links }; console.log("Location objects are: ", Lokationer); user_locations.push(Lokationer); // location_obj.push(Lokationer); }); }); return user_locations; } export default getAllDatabaseLocations;

This method always returns an empty array, even if the console inside the loop prints as i expected? How to use async and await property so as to return an array with all Lokationer objects inside on it.

The await would go before an async function or function that returns a promise. I can't speak to whether this would be applicable to your Firebase call, but if it is you would put await to the right of the = in the assignment, just before the call that you want to wait for a result from. So let ref = await Firebase.[...] — obermillerk
– obermillerk, Commented Feb 4, 2019 at 18:13

Alan Friedman · Accepted Answer · 2019-02-04 19:39:52Z

You'll need to return a new promise because of the asynchronous ref.on("value") callback.

function getAllDatabaseLocations() { return new Promise(resolve => { ref.on("value", function (snapshot) { ... // when done filling the array resolve(user_locations); }); }); } const userLocations = await getAllDatabaseLocations(); // user_locations

Thanks. I got it working. But I can't get all object pushed into user_locations array. Only few objects get pushed into user_locations.

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