Develop Reference

Firebase Promise Returning Undefined Data Javascript

I've followed several guides on how to correctly wait for the data from my ListFile() function. I have logged the output to the console in ListFile() so I know the data is correct. When I try and await for the function to complete and log the data, I get one of two outputs when experimenting with awaits and promises:
getData error: TypeError: undefined is not an object (evaluating 'response.json')
or
Promise {
"_U": 0,
"_V": 0,
"_W": null,
"_X": null,
}
I'm creating a React Native app and the function that calls ListFile() contains a bunch of other components that are rendered so I can't make the entire function an async function. Not sure what else to do here.
Calls ListFile()
const getData = async () => {
try {
const response = await ListFile();
const data = response.json();
console.log(data);
} catch (err) {
console.log("getData error: " + err);
}
}
getData(); //always returns getData error: TypeError: undefined is not an object (evaluating 'response.json')
ListFile()
async function ListFile() {
// Reference Firebase Container
var filesInStorageList = [];
let content = [];
const listRef = ref(fbStorage, filePath);
console.log("Listing Files");
// List all files in container
listAll(listRef)
.then((res) => {
res.prefixes.forEach((folderRef) => {
// All the prefixes under listRef.
// You may call listAll() recursively on them.
console.log(res);
});
res.items.forEach((itemRef) => {
// All the items under listRef.
let fileInStorage = itemRef["_location"]["path_"].slice(filePath.length);
filesInStorageList.push(fileInStorage);
// CORRECT DATA IS LOGGED console.log("Pushing " + fileInStorage);
// CORRECT DATA IS LOGGED console.log(filesInStorageList);
});
return filesInStorageList;
}).catch((error) => {
// Uh-oh, an error occurred!
console.log("ListFile - ERROR");
});
}

You're mixing async/await and Promises. Although they serve similar purposes, generally they are used separately to avoid situations like this where they are used together and then create unexpected results if one doesn't know what to look for.
You annotate your ListFile function with async, which means that it's expecting to find await somewhere. Instead, you use a Promise-based .then and .catch.
To convert your code, you could change it to this:
async function ListFile() {
// Reference Firebase Container
var filesInStorageList = [];
let content = [];
const listRef = ref(fbStorage, filePath);
console.log("Listing Files");
// List all files in container
try {
const res = await listAll(listRef);
//...do your forEach loops
return filesInStorageList;
} catch(err) {
//handle your error
}
}

You should add a return on the listAll method to return its value when calling it from getData(). See sample code below:
const getData = async () => {
try {
ListFile()
.then((response) => {
// do something here.
console.log(response);
});
} catch (err) {
console.log("getData error: " + err);
}
}
getData();
async function ListFile() {
// Reference Firebase Container
var filesInStorageList = [];
let content = [];
const filePath = "test/";
const listRef = ref(storage, filePath);
// List all files in container
return listAll(listRef)
.then((res) => {
res.prefixes.forEach((folderRef) => {
// All the prefixes under listRef.
// You may call listAll() recursively on them.
console.log(res);
});
res.items.forEach((itemRef) => {
// All the items under listRef.
let fileInStorage = itemRef["_location"]["path_"].slice(filePath.length);
filesInStorageList.push(fileInStorage);
// CORRECT DATA IS LOGGED console.log("Pushing " + fileInStorage);
// CORRECT DATA IS LOGGED console.log(filesInStorageList);
// console.log(filesInStorageList);
});
return filesInStorageList;
}).catch((error) => {
// Uh-oh, an error occurred!
console.log(error);
});
}
Also, as #jnpdx stated, you have to use a Promise-based .then and .catch on your ListFile()

Promises not getting resolved

I am running this asynchronous function in my React app -
const getMetaData = async (hashes: any) => {
console.log({ hashes });
try {
const data = hashes.map(async (hash: any) => {
const url = `http://localhost:3003/user/pinata/getmetadata/${hash}`;
const metadata = await axios.get(url);
return metadata.data.response;
});
console.log("data1", data);
const metadata = await Promise.all(data);
console.log('data2', metadata);
} catch (error) {
console.log('getMetaData Error', error);
}
};
console.log("data1", data) gives me -
data1 (12) [Promise, Promise, Promise, Promise, Promise, Promise, Promise, Promise, Promise, Promise, Promise, Promise]
The problem here is after I do a await Promise.all(data) I don't get data2 anywhere in the console. Maybe because the Promises are not even getting resolved?
Any idea what might be wrong?
Thanks in advance.

It seems that your code works fine when using SWAPI API so it can be that the API you use does not deliver data appropriately. I run the below code to test. Here's a link to codebox to play around with it if you want.
import axios from "axios";
const data = ["people", "planets", "starships"];
const getMetaData = async (hashes) => {
console.log({ hashes });
try {
const data = hashes.map(async (hash) => {
const url = `https://swapi.dev/api/${hash}`;
const metadata = await axios.get(url);
return metadata.data.results;
});
console.log("data1", data);
const metadata = await Promise.all(data);
console.log("data2", metadata);
} catch (error) {
console.log("getMetaData Error", error);
}
};
getMetaData(data);

With this code, it appears the most likely situation is that one of the promises in the loop is not resolving or rejecting. To confirm that, you can log every possible path with more local error handling so you can see exactly what happens to each request. I also added a timeout to the request so you can definitely find out if it's just not giving a response, but you can also see that by just looking at the logging for begin and end of each request in the loop:
function delay(msg, t) {
return new Promise((resolve, reject)) => {
setTimeout(() => {
reject(new Error(msg));
}), t);
});
}
const getMetaData = async (hashes: any) => {
console.log({ hashes });
try {
const data = hashes.map(async (hash: any, index: number) => {
try {
console.log(`Request: ${index}, hash: ${hash}`);
const url = `http://localhost:3003/user/pinata/getmetadata/${hash}`;
const metadata = await axios.get(url);
console.log(`Request: ${index}, result: ${metadata.data.response}`);
return metadata.data.response;
} catch (e) {
console.log(`Request: ${index} error: `, e);
throw e;
}
});
console.log("data1", data);
const metadata = await Promise.all(data.map((p: any, index: number) => {
return Promise.race(p, delay(`Timeout on request #${index}`, 5000));
});
console.log('data2', metadata);
} catch (error) {
console.log('getMetaData Error', error);
}
};
FYI, I don't really know Typescript syntax so if I've made any Typescript mistakes here, you can hopefully see the general idea and fix the syntax.

Vuex action not waiting to finish axios promise

I encounter a strange situation developing an application in Laravel + VueJS/Vuex stack.
I understand that if a promise is not returned the parent function calling it will not wait for it to resolve so things will go asynchronous. Axios returns a promise by default when calling a resourse through http.
So i have the parent function which looks like this:
fetchInvoiceSeries() {
var arr = []
let invsrs = this.$store.getters['getInvoiceSeries']
if (invsrs == null) {
return this.$store
.dispatch('get_invoice_series')
.then(() => {
invsrs = this.$store.getters['getInvoiceSeries']
if (invsrs != null) {
invsrs.forEach(function(s) {
arr.push({
value: s.id,
text: s.series + ' / ' + s.increment
})
})
this.series = arr
} else {
console.log('Error while fetching invoice series!')
}
})
.catch(e => {
console.log(e)
})
} else {
invsrs.forEach(function(s) {
arr.push({
value: s.id,
text: s.series + ' / ' + s.increment
})
})
this.series = arr
}
}
And here is the function defined in action part of the vuex module:
get_invoice_series({ commit }) {
return get('/api/series/0')
.then(response => {
if (response.data && typeof response.data !== undefined) {
let payload = response.data
commit('SET_INVOICE_SERIES', payload)
} else {
console.log('error', error)
}
})
.catch(error => {
console.log('error', error)
})
},
So as you can see i am returning the get request from axios inside the action. In the parent i am calling the action and the "then" keyword in order to do some processing after the action it's done. Also i am using arrow function because i need the context in the parent function in order to call this.$store ...
The problem is that even after checking the getter to see if the state have the invoice series and getting them using the get_invoice_series action i still don't have the invoice series in memory judging by the code i wrote. The console keeps loggin 'Error while fetching invoice series!' the first time i execute the code and the second time (after the information exists in state), the code skips fetching the invoice series (as expected).
Can you tell me what i am doing wrong ? Thank you!

Your error comes from invsrs being null the first time, and not null the second time.
This means that your function get_invoice_series({ commit }) is asynchronous, and that it returns a promise.
For more readability, maybe you should make your call independently from your return statement, using async/await expressions :
async get_invoice_series({ commit }) {
const response = await get('/api/series/0')
if (response.data === undefined) return null
const payload = response.data
commit('SET_INVOICE_SERIES', payload)
return payload
},
And then make your calls wait for this fetch to process :
async fetchInvoiceSeries() {
let arr = []
const invsrs = await this.$store.getters['getInvoiceSeries']
// ...
It's pure conjecture here, let me know if it helps or not.

Async method not waiting for a function - VUE

i'm having this error and haven't got to resolve it though have researched a lot in MDN and here. As title saysinto VUE i'm trying to use async and await but js is not waiting the 'await' function to end. Here it is:
methods: {
async search (terms, done) {
console.log('1.')
this.filter = this.$refs.chipsInput.input
await this.loadtags()
console.log('3.')
done(this.tagsList)
},
loadtags () {
this.$axios
.get('/api/tags/?id__icontains=&id=&name__icontains=' + this.filter + '&name=&ordering=name&page_size=20')
.then(response => {
console.log('2.', response.data.results)
let temp = response.data.results
this.tagsList = temp.map(obj => {
return {
name: obj.name,
label: obj.name,
value: obj.name,
idField: obj.id
}
})
})
},
I am not able to post pictures yet, but add a link where you can look the console log where js prints the '3.' (which is placed after the await call) before '2.':
Image:
console
¿What am i doing wrong? already tried modifying the await like this:
let foo = await this.loadtags() and including a 'return 0' at the end of loadtags function but didn't work for me. Probably is a dumb thing, excuse me for that.

You aren't returning anything from the loadtags method, so the code doesn't wait.
Change this:
loadtags () {
this.$axios
.get(...
To this:
loadtags () {
return this.$axios
.get(...
async/await is more or less just sugar over Promises, so returning the Promise gives you something to await in the other method.

This is how I resolved this in my Vue application.
Before a user submits a new "tag" with submitNewTag() I need to check if it exists already in the list of tags, using async theTagExists().
submitNewTag() {
this.clearError();
this.theTagExists().then((res) => {
if (!res) {
console.log("TAG DOES NOT EXIST, SO ADD IT TO THE DATABASE");
this.saveTagToDatabase();
}
});
},
async theTagExists() {
console.log("CHECKING IF A TAG EXISTS");
await axios.get(`${this.apiUrl}/alltags`).then((res) => {
console.log("CHECKING IS DONE");
this.tagExists = res.data.allTags.some(
res =>
res.name.trim().toLowerCase() ===
this.newTag.tagName.trim().toLowerCase()
);
});
console.log("RETURN THE RESULT");
return this.tagExists;
},

Data initializing with promises

I really struggle with data initializing and promises. I am using Ionic 3 with Angular and Ionic storage, but my question is mainly related to how promises operate.
Basically I would like to achieve the following:
when my app starts it should use the local storage collection
if the local storage collection does not exist or is empty, create a new one with http
if the http fails, create a collection with local data.
My solution so far:
getNewsItems():Promise<any> {
return this.storage.get(this.newsKey).then((data) => {
if(data == null)
{
return (this.buildNewsItemsViaHttp());
} else {
return (data);
}
});
}
private buildNewsItemsViaHttp(){
return new Promise(resolve => {
this.http.get('some/url/to/fetch/data')
.subscribe(
data => {
this.newsCollection = data;
this.storage.set(this.newsKey, this.newsCollection);
resolve(this.newsCollection);
},
(err) => {
resolve (this.buildNewsItemsViaLocalJSON());
}
);
});
}
private buildNewsItemsViaLocalJSON() {
return new Promise(resolve => {
this.http.get('assets/data/newsCollectionLocal.json')
.subscribe(
data => {
this.newsCollection = data;
this.storage.set(this.newsKey, this.newsCollection);
resolve(this.newsCollection);
},
(err) => {
console.log(err);
}
);
});}
I don't like some parts of it, for example returning a promise inside a promise - is this actually an issue?
Thanks in advance

A clean solution could be using async\await methods:
async buildNewsItemsViaHttp(){
return await this.http.get()....
}
async buildNewsItemsViaLocalJSON(){
return await this.http.get()....
}
async getNewsItems(){
return await this.storage.get()...
}
async getItems(){
return ((await this.getNewsItems()) || (await this.buildNewsItemsViaLocalJSON()) || (await this.buildNewsItemsViaHttp()));
}
usage:
const items = await this.getItems();
You can optimize the resources, cache them and return them in each function.
Example:
async buildNewsItemsViaHttp(){
let result = cache.get(); // todo
if(!result){
result = await this.http.get()...
cache.set(result)
}
return result;
}