I have this controller
const getBalance = async (address, network) => {
const web3 = getWeb3Instance(network);
const currentBalance = await web3.eth.getBalance(address);
const formattedBalance = web3.utils.fromWei(currentBalance, 'ether');
return formattedBalance
};
This is how I use it in the route:
router.post('/getBalance', (req, res) => {
const {address,network} = req.body
try {
res.status(200).send(controllers.getBalance(address,network))
} catch (e) {
res.status(404).send(`${e}`)
}
});
When I console.log(formattedBalance) it logs the correct answer but in the response it is sending empty object {} and I don't know why. I'm using node.js with express and web3.
Any suggestions please?
You have the word async infront of your function. An function has an different behaviour if you put async infront of it. It acts like an promise.
Did you tried console.log(controllers.getBalance(address,network))? In the browser you would see Promise { <pending> }
The problem is you sending an pending promise back.
Change it to this. You need to wait till the promise resolves
router.post('/getBalance', async (req, res) => {
const {address,network} = req.body
try {
let balance = await controllers.getBalance(address,network);
res.status(200).send(balance)
} catch (e) {
res.status(404).send(`${e}`)
}
});
Related
I'm having a little trouble getting back a result from an async function I am calling in a for loop, I should be getting back a string but it is returning a promise instead
I am following this syntax but I haven't been able to get it to work properly and I'm hoping for some insight into why this fails https://eslint.org/docs/rules/no-await-in-loop
here's the function I am trying to work with, in this case decodeTheObject is async and returns a promise but if I use await decodeTheObject eslint will give me an error saying I can't use await inside a for loop, unfortunately the workaround above still results in a promise being returned instead of a resolved value
async function decode (request, encodedObj) {
const decodedArr = [];
try{
for (const id of encodedObj) {
decodedArr.push({
data: decodeTheObject(request, id), // this is an async function
partial: true,
});
}
await Promise.all(decodedArr);
return decodedArr;
}catch (err) {
throwError(
req,
{
errorDetails: [
{
issue: 'INVALID_ENCODING',
description: 'Invalid encoded obj',
},
],
},
);
}
};
// ----- calling function -----
const decodedObj = await decode(request, encodedItem);
const payload = {
newprop: decodedObj
};
Promise.all() has to work directly on an array of promises. You are passing it an array of objects which won't know how to reach into the objects to get the promises so thus, it won't accomplish anything useful. There are a couple ways to approach this.
This will await each async call in sequence, get the value and push the value into the array:
async function decode (request, encodedObj) {
const decodedArr = [];
try{
for (const id of encodedObj) {
let data = await decodeTheObject(request, id);
decodedArr.push({data, partial: true});
}
return decodedArr;
} catch(e) {
...
}
}
Or, you could run them in parallel with Promise.all() like this by creating an array of promises and using Promise.all() on that array:
async function decode (request, encodedObj) {
return Promise.all(encodedObj.map(id => {
return decodeTheObject(request, id).then(data => {
return {data, partial: true};
});
})).catch(err => {
...
});
}
I'm new to fetching and posting data using an API, and I can't work out how to do something once my Post has been completed.
I have a function that calls the API with the Post data. I need to set the loading state to false once the Post has been completed. Everything works apart from that, the data gets sent to Mongo, I just need to turn off my loading spinner once it has completed.
How do I do this, please?
This is how I'm trying to do it:
const postData = async () => {
setLoading(true)
await axios.post('/api/addData',form)
.then(response => {
setLoading(false)
})
}
And this is the API bit:
import { connectToDatabase } from "util/mongodb"
export default async (req, res) => {
const { db } = await connectToDatabase()
await db
.collection("posts")
.insertOne(req.body);
}
There is two potential problem in your code, first you're not sending any data back to the front in your backend code. Usually you send back the id of the inserted element (It can be usefull to do some mutation in your front), you'll also need to try catch your call to the db to notify that something went wrong to the front end side :
import { connectToDatabase } from "util/mongodb"
export default async (req, res) => {
try {
const { db } = await connectToDatabase()
const insertedPost = await db
.collection("posts")
.insertOne(req.body);
res.status(201).send(insertedPost.insertedId);
// again it's up to you to know what can be usefull to your front-end to use
// Look at http status code online to know what's the best fit
} catch (err) {
res.status(500).send(err.message);
// send whatever that can be usefull for your front end to handle the error
}
}
In your front-end code you're using await with .then, it's weird usage. You can put your setLoading(false) after the await without the .then but you'll still need to try catch it. What I prefer to do is using the finally block to stop loading, so if my api call fail the loading is still stopped :
const postData = async () => {
setLoading(true)
try {
const response = await axios.post('/api/addData',form)
// do something with response
} catch (err) {
// notify user that something went wrong
} finally {
setLoading(false);
}
}
const postData = () => {
setLoading(true)
axios.post('/api/addData',form)
.then(response => {
// do something with response
})
.catch((err) => {
// notify user that something went wrong
})
.finally(() => {
setLoading(false);
})
}
Building a NodeJS REST API.
Trying to send load data from FireBase collection, then sending it to the user (as API response).
Looks like the problem is that it's not waits for the firebase fetch to resolve, but send back a response without the collection data. (tried to use ASYNC-AWAIT but its not working)
exports.getChatMessages = async (req, res, next) => {
const chatId = req.params.chatId
const getChatData = () => {
db
.collection('chats')
.doc(chatId)
.collection('messages')
.orderBy('timeStamp', 'asc')
.onSnapshot((snapshot) => {
snapshot.docs.forEach(msg => {
console.log(msg.data().messageContent)
return {
authorID: msg.data().authorID,
messageContent: msg.data().messageContent,
timeStamp: msg.data().timeStamp,
}
})
})
}
try {
const chatData = await getChatData()
console.log(chatData)
res.status(200).json({
message: 'Chat Has Found',
chatData: chatData
})
} catch (err) {
if (!err.statusCode) {
err.statusCode(500)
}
next(err)
}
}
As you can see, I've used 2 console.logs to realize what the problem, Terminal logs looks like:
[] (from console.logs(chatData))
All messages (from console.log(msg.data().messageContent))
Is there any way to block the code unti the firebase data realy fetched?
If I correctly understand, you want to send back an array of all the documents present in the messages subcollection. The following should do the trick.
exports.getChatMessages = async (req, res, next) => {
const chatId = req.params.chatId;
const collectionRef = db
.collection('chats')
.doc(chatId)
.collection('messages')
.orderBy('timeStamp', 'asc');
try {
const chatsQuerySnapshot = await collectionRef.get();
const chatData = [];
chatsQuerySnapshot.forEach((msg) => {
console.log(msg.data().messageContent);
chatData.push({
authorID: msg.data().authorID,
messageContent: msg.data().messageContent,
timeStamp: msg.data().timeStamp,
});
});
console.log(chatData);
res.status(200).json({
message: 'Chat Has Found',
chatData: chatData,
});
} catch (err) {
if (!err.statusCode) {
err.statusCode(500);
}
next(err);
}
};
The asynchronous get() method returns a QuerySnapshot on which you can call forEach() for enumerating all of the documents in the QuerySnapshot.
You can only await a Promise. Currently, getChatData() does not return a Promise, so awaiting it is pointless. You are trying to await a fixed value, so it resolves immediately and jumps to the next line. console.log(chatData) happens. Then, later, your (snapshot) => callback happens, but too late.
const getChatData = () => new Promise(resolve => { // Return a Promise, so it can be awaited
db.collection('chats')
.doc(chatId)
.collection('messages')
.orderBy('timeStamp', 'asc')
.onSnapshot(resolve) // Equivalent to .onSnapshot((snapshot) => resolve(snapshot))
})
const snapshot = await getChatData();
console.log(snapshot)
// Put your transform logic out of the function that calls the DB. A function should only do one thing if possible : call or transform, not both.
const chatData = snapshot.map(msg => ({
authorID: msg.data().authorID,
messageContent: msg.data().messageContent,
timeStamp: msg.data().timeStamp,
}));
res.status(200).json({
message: 'Chat Has Found',
chatData
})
Right now, getChatData is this (short version):
const getChatData = () => {
db
.collection('chats')
.doc(chatId)
.collection('messages')
.orderBy('timeStamp', 'asc')
.onSnapshot((snapshot) => {}) // some things inside
}
What that means is that the getChatData function calls some db query, and then returns void (nothing). I bet you'd want to return the db call (hopefully it's a Promise), so that your await does some work for you. Something along the lines of:
const getChatData = async () =>
db
.collection('chats')
// ...
Which is the same as const getChatData = async() => { return db... }
Update: Now that I've reviewed the docs once again, I see that you use onSnapshot, which is meant for updates and can fire multiple times. The first call actually makes a request, but then continues to listen on those updates. Since that seems like a regular request-response, and you want it to happen only once - use .get() docs instead of .onSnapshot(). Otherwise those listeners would stay there and cause troubles. .get() returns a Promise, so the sample fix that I've mentioned above would work perfectly and you don't need to change other pieces of the code.
I'm building a Slackbot that makes a call to an Express app, which then needs to 1) fetch some other data from the Slack API, and 2) insert resulting data in my database. I think I have the flow right finally using async await, but the operation is timing out because the original call from the Slackbot needs to receive a response within some fixed time I can't control. It would be fine for my purposes to ping the bot with a response immediately, and then execute the rest of the logic asynchronously. But I'm wondering the best way to set this up.
My Express route looks like:
const express = require('express');
const router = express.Router();
const knex = require('../../db/knex.js');
const slack = require('../../services/slack_helpers');
// POST api/slack/foo
router.post('/foo', async (req, res) => {
let [body, images] = await slack.grab_context(req);
knex('texts')
.insert({ body: body,
image_ids: images })
.then(text => { res.send('worked!'); }) // This sends a response back to the original Slackbot call
.catch(err => { res.send(err); })
});
module.exports = router;
And then the slack_helpers module looks like:
const { WebClient } = require('#slack/web-api');
const Slack = new WebClient(process.env.SLACKBOT_TOKEN);
async function grab_context(req) {
try {
const context = await Slack.conversations.history({ // This is the part that takes too long
channel: req.body.channel_id,
latest: req.headers['X-Slack-Request-Timestamp'],
inclusive: true,
limit: 5
});
} catch (error) {
return [error.toString(), 'error'];
}
return await parse_context(context);
};
function parse_context(context) {
var body = [];
context.messages.forEach(message => {
body.push(message.text);
});
body = body.join(' \n');
return [body, ''];
}
module.exports = {
grab_context
};
I'm still getting my head around asynchronous programming, so I may be missing something obvious. I think basically something like res.send perhaps needs to come before the grab_context call? But again, not sure the best flow here.
Update
I've also tried this pattern in the API route, but still getting a timeout:
slack.grab_context(req).then((body, images) => {
knex ...
})
Your timeout may not be coming from where you think. From what I see, it is coming from grab_context. Consider the following simplified version of grab_context
async function grab_context_simple() {
try {
const context = { hello: 'world' }
} catch (error) {
return [error.toString(), 'error']
}
return context
}
grab_context_simple() /* => Promise {
<rejected> ReferenceError: context is not defined
...
} */
You are trying to return context outside of the try block where it was defined, so grab_context will reject with a ReferenceError. It's very likely that this error is being swallowed at the moment, so it would seem like it is timing out.
The fix is to move a single line in grab_context
async function grab_context(req) {
try {
const context = await Slack.conversations.history({
channel: req.body.channel_id,
latest: req.headers['X-Slack-Request-Timestamp'],
inclusive: true,
limit: 5
});
return await parse_context(context); // <- moved this
} catch (error) {
return [error.toString(), 'error'];
}
};
I'm wondering the best way to set this up.
You could add a higher level try/catch block to handle errors that arise from the /foo route. You could also improve readability by staying consistent between async/await and promise chains. Below is how you could use async/await with knex, as well as the aforementioned try/catch block
const express = require('express');
const router = express.Router();
const knex = require('../../db/knex.js');
const slack = require('../../services/slack_helpers');
const insertInto = table => payload => knex(table).insert(payload)
const onFooRequest = async (req, res) => {
try {
let [body, images] = await slack.grab_context(req);
const text = await insertInto('texts')({
body: body,
image_ids: images,
});
res.send('worked!');
} catch (err) {
res.send(err);
}
}
router.post('/foo', onFooRequest);
module.exports = router;
I'm having some trouble with the Koa framework. I'm trying to build a pretty basic server by I'm having a problem with my router. The ctx always return 404 despite passing in my functions.
Some code :
//www.js
const Koa = require('koa');
const app = new Koa();
const version = require('./routes/version');
app.listen(config.port, () => {
console.log('Server is listenning on port ' + config.port);
});
app.use(version.routes());
app.use(ctx => {
console.log ('test')
});
//version.js
const Router = require('koa-router');
const router = new Router();
router.prefix('/version');
router.use((ctx, next) => {
ctx.vFactory = new VersionFactory(ctx.app.db);
next();
});
router.get('/', getAllVersions);
async function getAllVersions(ctx, next) {
const ret = await ctx.vFactory.getAllVersions();
ctx.body = JSON.stringify(ret.recordset);
console.log(ctx.body)
await next();
}
I've checked a few threads. Most of the time, the problem seems to come from a non Promise based function in the await part of the router function. Here it is a simple DAO using mssql which is pretty promise based.
class DaoVersion {
constructor(db) {
this.pool = db;
}
async getAllVersions() {
const me = this;
return new Promise((resolve) => {
const ret= me.pool
.query(getVersion);
resolve(ret);
});
}
}
The console output seems good. I have my ctx.body set with my db data but if I try to check the whole context, I still have a 404. More interesting, if I try to ctx.res.write (using default node response) I got the "already end" message. So it seems Koa have sent the message before passing threw my function.
Any idea why and how I could correct that ?
Koa default response.status code is 404, unlike node's res.statusCode which defaults to 200.
Koa changes the default status code to 200 - when your route set's a non empty value to ctx.body or in some cases you can manually change (like if you need to set it to 202) it by using ctx.status = xxx.
You can use this documentation for reference: https://github.com/koajs/koa/blob/master/docs/api/response.md
Also, your route should be an async function:
router.get('/', async(ctx, next) => {
ctx.body = await getAllVersions
await next()
}