I can console log userData.name and userData.summonerLevel just fine, but why can't I return userData as an object?
I am trying to assign the returned object to a variable, but I really don't understand why it doesn't work.
function getStats() {
https.get(https://euw1.api.riotgames.com/lol/summoner/v3/summoners/by-name/yojimbozx?api_key=${API_KEY},
(res) => {
let userData = ''
res.on('data', (chunk) => {
userData += chunk
})
res.on('end', () => {
userData = JSON.parse(userData)
if(!userData.hasOwnProperty('status')) {
console.log(userData.name, userData.summonerLevel)
return userData
}
return console.log("Summoner not found")
})
}).on("error", (err) => {
return console.log("Error: " + err.message)
})
}
You can, but since you are doing some async stuff you should have your function getStats () return the http call and it should work. Currently you are returning the outcome of the call to the function, but the function is not returning anything
Related
I'm trying to send a GET request, parse its response and return it to another method. Apparently I have problems handling the asynchronous response.
I want to use Node.js' standard modules, so no Axios.
// class 1: Calling API, processing and returning the response
export async function getData() {
let str = '';
const options = {
hostname: 'jsonplaceholder.typicode.com',
path: '/posts/',
method: 'GET',
json: true,
};
https
.get(options, response => {
response.on('data', chunk => {
str += chunk;
});
response.on('end', () => {
return parseJson(str);
});
})
.on('error', error => {
console.log(error);
});
}
async function parseJson(str) {
const json = JSON.parse(str);
var text;
try {
json.forEach(element => {
text += element.body;
});
// console.log(text); // I'm getting the expected output
return text;
} catch (error) {
console.log('error');
}
}
// class 2: Calling the 2 methods above
getData().then(function (value) {
console.log('DATA: ' + value); // this is called first
});
Unfortunately as output I get an undefined. Despite using async and then:
DATA: undefined
Change getData as follows
export function getData() {
return new Promise((resolve, reject) => {
let str = '';
const options = {
hostname: 'jsonplaceholder.typicode.com',
path: '/posts/',
method: 'GET',
json: true,
};
https.get(options, response => {
response.on('data', chunk => {
str += chunk;
});
response.on('end', () => {
try {
const result = parseJson(str);
resolve(result);
} catch (error) {
reject(error);
}
});
response.on('error', reject);
})
.on('error', reject);
});
}
Now it returns a Promise, which resolves to the result of parseJson(str) or rejects with the error at on('error'
And parseJson as follows - doesn't need to be async since there's nothing asynchronous about the code inside it
Also, removing the try/catch in parseJson and using try/catch in .on("end" means that you can reject the promise returned by getData if there's an error in the parseJson call
function parseJson(str) {
const json = JSON.parse(str);
let text = '';
json.forEach(element => {
text += element.body;
});
return text;
}
alternatively (IMHO better)
function parseJson(str) {
const data = JSON.parse(str); // call it data, not json
return data.map(({body}) => body).join('');
}
or even
const parseJson = (str) => JSON.parse(str).map(({body}) => body).join('');
But that's not important :p
Looking to set the object that is retrieved from a https.get to a variable opposed to printing it to console. Attempting to use Promises to achieve this but it is just returning the function itself.
const https = require("https");
if(true){
const destinationsfinal = () => {
return new Promise((resolve,reject) => {
https
.get('https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY', (resp) => {
let data = '';
resp.on('data', (chunk) => {
data += chunk;
});
resp.on('end', () => {
resolve(JSON.parse(data))
});
})
.on('error', (err) => {
reject('Error: ' + err.message);
});
})
}
}
You have to resolve the promise in order to get the result from your function (that is because it returns a Promise and not the result of this promise). To solve this problem you can do it either with then/catch or async/await.
then/catch:
let result;
destinationsfinal()
.then((data) => {
result = data;
})
.catch((error) => {
console.log(error);
});
async/await:
let result;
(async () => {
try {
result = await destinationsfinal();
} catch (error) {
console.log(error);
}
})();
I have an issue with sending a request to backend from my componentDidMount(). Basically I need to do two things before rendering screen:
Obtain data from API call and save it to state
Send that obtained data to backend and take response values from backend.
The problem I've faced on first step is that setState() is async, and even though my array is not empty (I see it's elements in render() and componentDidUpdate fucntion) in componentDidMount() when I console.log() array it will be empty. Now, the issue is: I still need to send that state array to backend before showing the screen. But how can I do it, when it appears empty there?
I have everything working fine if I send the request from the Button element in my render function, but that's not exactly what I need. Any suggestions?
this.state = {
ActivityItem: [],
}
componentDidMount() {
this.getDataFromKit(INTERVAL); //get data from library that does API calls
this.sendDataToServer(); //sending to backend
}
componentDidUpdate() {
console.log("componentDidUpdate ", this.state.ActivityItem) // here array is not empty
}
getDataFromKit(dateFrom) {
new Promise((resolve) => {
AppleKit.getSamples(dateFrom, (err, results) => {
if (err) {
return resolve([]);
}
const newData = results.map(item => {
return { ...item, name: "ItemAmount" };
});
this.setState({ ActivityItem: [...this.state.ActivityItem, ...newData] })
})
});
And last one:
sendDataToServer() {
UserService.sendActivityData(this.state.ActivityItem).then(response => {
}).catch(error => {
console.log(error.response);
})
And here it works as expected:
<Button
title='send data!'
onPress={() => this.sendDataToServer()
} />
UPDATE
If I have like this (wrapped inside initKit function this will return undefined.
AppleKit.initKit(KitPermissions.uploadBasicKitData(), (err, results) => {
if (err) {
return;
}
return new Promise((resolve) => {
AppleKit.getSamples(dateFrom, (err, results) => {
if (err) return resolve([]);//rest is the same
you have to wait for the promise to resolve. You need something like this:
componentDidMount() {
this.getDataFromKit(INTERVAL).then(result => {
this.sendDataToServer(result); //sending to backend
}).catch(e => console.error);
}
and you can update your other function that fetches data to return it:
getDataFromKit(dateFrom) {
return new Promise((resolve) => {
AppleKit.getSamples(dateFrom, (err, results) => {
if (err) return resolve([]);
const newData = results.map(item => {
return { ...item, name: "ItemAmount" };
});
const allData = [ ...this.state.ActivityItem, ...newData ];
this.setState({ ActivityItem: allData });
resolve(allData);
});
});
}
finally, you need the 'sendData' function to not depend on state, but get a param passed to it instead:
sendDataToServer(data) {
UserService.sendActivityData(data).then(response => {
// ... do response stuff
}).catch(error => {
console.log(error.response);
});
}
Handling Multiple Requests
if the requests don't depend on each other:
componentDidMount() {
Promise.all([
promise1,
promise2,
promise3,
]).then(([ response1, response2, response3 ]) => {
// do stuff with your data
}).catch(e => console.error);
}
if the requests do depend on each other:
componentDidMount() {
let response1;
let response2;
let response3;
promise1().then(r => {
response1 = r;
return promise2(response1);
}).then(r => {
response2 = r;
return promise3(response2);
}).then(r => {
response3 = r;
// do stuff with response1, response2, and response3
}).catch(e => console.error);
}
as far as your update, it seems like you wrapped your async request in another async request. I'd just chain it instead of wrapping it:
make the initKit a function that returns a promise
function initKit() {
return new Promise((resolve, reject) => {
AppleKit.initKit(
KitPermissions.uploadBasicKitData(),
(err, results) => {
if (err) reject({ error: 'InitKit failed' });
else resolve({ data: results });
}
);
});
}
make get samples a separate function that returns a promise
function getSamples() {
return new Promise((resolve) => {
AppleKit.getSamples(dateFrom, (err, results) => {
if (err) resolve([]); //rest is the same
else resolve({ data: results });
});
});
}
chain 2 promises back to back: if initKit fails, it will go in the .catch block and getSamples wont run
componentDidMount() {
initKit().then(kit => {
return getSamples();
}).then(samples => {
// do stuff with samples
}).catch(e => console.log);
}
I have a problem to send string that is from s3 object body to a client
I'm using aws sdk for node, and apollo server(express), express, react
I did get object from s3 and create readable stream. and then i listen data event so I might send string to a client
let data = '';
s3.getObject(params).createReadStream().on('data', function(chunk) {
data += chunk;
});
return { data }
I thought data is not a empty string but it is empty string
what can I do to solve the problem?
Edit:
let data = '';
function promiseBasedRequest (params) {
return new Promise((resolve, reject) => {
s3.getObject(params).createReadStream()
.on('data', function (chunk) {
data += chunk;
})
.on('end', function () {
resolve(data);
})
.on('error', function (err) {
reject(err);
});
});
}
await promiseBasedRequest(params);
This works as I intended.
You are not waiting for the writing to end. First the function need to be asynchronous a promise or callback.
function getData(params) {
let data = ''
return new Promise((res, rej) => {
let data = '';
s3.getObject(params).createReadStream()
.on('data', function (chunk) {
data += chunk;
})
.on('end', function(){
res(data);
})
.on('error', function(){
rej()
})
})
}
You can use the function by:
(async(){
const data = await getData()
})();
Or getData().then(..)
EDIT: Also, getObject has one promise method as well.
s3.getObject(params).promise().then(...).catch(...)
I'm calling a function inside a then statement, and that function has to wait for an event to fire, but my initial function is returning undefined almost immediately:
// call.js
const dialogflow = require('./dialogflow')
module.exports = {
receive: functions.https.onRequest((request, response) => {
...
let respondToUser = getUserId
.then((uid) => {
payload.uid = uid
dialogflow.handleIncoming(payload).then((result) => {
console.log(result)
})
})
.then((result) => {
console.log(result)
response.end()
})
...
}
}
// dialogflow.js
module.exports = {
handleIncoming: (payload) => {
...
let df = dialogflow.textRequest(message.message, {
sessionId: payload.from
})
.on('response', (response) => {
return response.result.fulfillment.speech
})
.on('error', (error) => {
return 'That\'s an error on my end. Try again later!'
})
.end()
}
}
The goal is to call dialogflow.handleIncoming(payload) from call.js, wait for it to return some text, and then continue. But no matter how I have structured it, receive just keeps blowing through it and dialogflow.handleIncoming(payload) ends up undefined.
I've tried using a promise on df with no success, and I can't figure out how to make respondToUser wait for a full response from handleIncoming. Everything else is working so I'm only including relevant code.
This is using api.ai (dialogflow), but in cloud functions in Firebase if that helps. Appreciate any help!
Problem is dialogflow.handleIncoming(payload) is not structured for async. Try this:
// dialogflow.js
exports.handleIncoming = (payload) =>
new Promise((resolve, reject) => {
...
let df = dialogflow.textRequest(message.message, {
sessionId: payload.from
})
.on('response', (response) => {
resolve(response.result.fulfillment.speech)
})
.on('error', (error) => {
reject ('That\'s an error on my end. Try again later!')
})
.end()
}
Your receive function isn't waiting for dialogflow.handleIncoming(payload) to complete. The then function that contains it doesn't have a return statement, so it's returning undefined rather than returning the result of dialogflow.handleIncoming (which is what you want).
let respondToUser = getUserId
.then((uid) => {
payload.uid = uid
return dialogflow.handleIncoming(payload)
})
.then((result) => {
console.log(result)
response.end()
})
The next then statement will contain the response from diagflow.handleIncoming.