This is the current code and what I've come up with:
function getToken() {
return new Promise(async (resolve, reject) => {
try {
let res = await fetch(url);
if (res.status === 418) {
setTimeout(getToken, 1000);
} else {
let token = await res.text();
console.log("1", token);
resolve(token);
}
} catch(e) {
reject(e);
}
});
}
async function test() {
let token = await getToken();
console.log("2", token);
}
test();
It logs 1 <token> but it doesn't log the other part like its supposed to (2 <token>). Is there something I'm missing or doing wrong?
My very naive approach would be a mix of a "sleep" function and standard async/await syntax (no need to mix then into it).
This does not take into consideration a possible infinite loop if the URL consistently returns a 418 http code.
The biggest thing to note is that I am returning getToken() in the retry and also returning token in the else. If we don't do this token inside test will always be undefined.
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
async function getToken() {
try {
let res = await fetch('https://httpstat.us/200');
if (res.status === 418) {
await sleep(1000);
return getToken();
} else {
let token = await res.text();
console.log("1", token);
return token;
}
} catch (e) {}
};
async function test() {
let token = await getToken();
console.log("2", token);
}
test();
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
function get(url, retryStatusCode) {
return new Promise(async (resolve, reject) => {
let found = false;
while (found !== true) {
try {
await sleep(1000);
await fetch(url).then(res => {
let text = res.text();
let status = res.status;
if (status !== retryStatusCode) {
found = true;
resolve(text);
}
});
} catch (error) {
reject(error);
}
}
});
};
Then await get(url, 404).
Use then
await fetch(url).then(res=>console.log(res).catch(err=>console.log(err);
I'm just logging the res here, you can do whatever you want with it
Related
How to return a Promise from the multiple axios get requests?
I have below code.
async function main() {
const URL_1 = 'abc.com/get1/data1';
const result_1 = await getData(URL_1);
const URL_2 = 'abc.com/get2/data2';
const result_2 = await getData(URL_2);
}
async function getData(dataURI) {
let getURI = dataURI;
const config = {
headers: {
Authorization: `Bearer ${my-token-text}`,
},
};
var finalData = [];
// until we get the next URL keep sending the requests
while (getURI != null) {
try {
const getResult = await axios.get(getURI, config);
if (getResult.status === 200) {
const receivedData = getResult.data.value;
finalData.push(...receivedData);
// check if we have nextLink in the payload
if (Object.prototype.hasOwnProperty.call(getResult.data, 'nextLink')) {
getURI = getResult.data.nextLink;
} else {
getURI = null;
return finalData;
}
}
} catch (err) {
break;
}
}
return null;
}
What I am trying to achieve is:
async function main() {
const URL_1 = 'abc.com/get1/data1';
const result_1 = getData(URL_1);
promisesArray.push(result_1);
const URL_2 = 'abc.com/get2/data2';
const result_2 = getData(URL_2);
promisesArray.push(result_2);
await Promise.allSettled(promisesArray).then((results) => {
console.log('Promise All Done: ', results);
});
}
This why I can perform all the requests in parallel.
But when I update the function getData(dataURI) to return return new Promise then I get error for await axios.
async function getData(dataURI) {
return new Promise((resolve, reject) => {
// Same code as above
});
}
I get error:
SyntaxError: await is only valid in async function
As Promise is not async I cannot await in the Promise.
Have you tried:
return new Promise(async (resolve, reject) => {
// Same code as above
});
I have the code below:
service.js
module.exports = {
getUser
};
async function getUser({ data }) {
return new Promise((resolve, reject) => {
const id = data["id"];
const doc = await db.collection('users').where('id', '==', id).get();
if (!doc.exists) {
resolve('No such document!');
} else {
resolve(doc.data());
}
});
}
controller.js
async function getUser(req, res, next) {
userService.getUser({ data: req.body }).then(function (val) {
res.json(val);
});
}
This throws an error: SyntaxError: await is only valid in async functions and the top level bodies of modules. How can I retrieve the data from the await in an effective manner?
You can use await only inside async function.
function dummy() {
return new Promise((res, rej) => {
setTimeout(() => {
res(20)
}, 300)
})
}
let val = new Promise(async(resolve, reject) => {
let v = await dummy()
resolve(v)
})
val.then(value => console.log(value))
I have the following function that works fine, except I need to wait until it finishes to execute the next statement:
zohoAuth.zoho_oAuth = function () {
// return new Promise((resolve, reject) => {
zohoAuth.state = utils.uuid();
const url = zohoAuth.authorizationURL();
zohoAuth.popUp(url);
getAuthCodeFromCatalyst();
//setTimeout(getAuthCodeFromCatalyst,1000);
function getAuthCodeFromCatalyst() {
return new Promise(function (resolve, reject) {
(async function waitForFoo() {
const gotAuthState = await zohoAuth.getUserDataFromStorageState(zohoAuth.state)
await gotAuthState;
if (gotAuthState) return resolve();
setTimeout(waitForFoo, 1000);
})();
});
}
console.log("bottom of zoho auth")
return true;
// });
}
I call the function with this:
zohoAuth.zoho_oAuth();
console.log("done waiting");
How do i wait for this to finish?
You're making this harder on yourself. Make sure to avoid the explicit promise constructor anti-pattern -
zohoAuth.zoho_oAuth = function () {
zohoAuth.state = utils.uuid();
const url = zohoAuth.authorizationURL();
zohoAuth.popUp(url);
return zohoAuth.getUserDataFromStorageState(zohoAuth.state);
}
You can access the result by attaching a .then handler to the result of your function call -
zohoAuth.zoho_oAuth()
.then(authState => console.log("bottom of auth state", authState))
.catch(console.error)
If you want to use async and await, go ahead. If an error occurs, don't catch it. Instead allow it to bubble up and be handled by the caller -
async function doAuth (...) {
const authState = await zohoAuth.zoho_oAuth()
console.log("received auth state", authState)
return "done" // or whatever
})
doAuth().then(console.log, console.error)
You should consider awaiting on the promise. Below snippet shows the difference of using await -
const asyncFunction = function() {
return new Promise(function(resolve, reject) {
setTimeout(() => {
console.log('inside promise');
resolve();
}, 100);
});
}
function callWithoutAwait() {
asyncFunction();
console.log('after without await function');
}
callWithoutAwait();
async function callWithAwait() {
await asyncFunction();
console.log('after with await function');
}
callWithAwait();
I was able to accomplish what I needed below is the code. Thanks for the help!
zohoAuth.zoho_oAuth = function() {
zohoAuth.state = utils.uuid();
const url = zohoAuth.authorizationURL();
zohoAuth.popUp(url);
return new Promise(function (resolve, reject) {
(async function waitForFoo() {
const gotAuthState = await zohoAuth.getUserDataFromStorageState(zohoAuth.state)
await gotAuthState;
if (gotAuthState) return resolve();
setTimeout(waitForFoo, 1000);
})();
});
}
And this is the call:
zohoAuth.zoho_oAuth()
.then(authState => console.log("bottom of auth state", authState))
.catch(console.error)
I have a function who send a message to the server to get the answer and if the answer is true I want my application to send an error to the user. The problem is that I can't manage to await the callback in the Fetch function I wrote.
This is the function who send the question to the server.
async donglePaired(){
if (Platform.OS !=='ios'){
var pairedDevices = await BluetoothScanner.getPairedDevices();
console.log('Sending........');
let data={
data:pairedDevices,
};
new Api().fetch("bluetoothCheck",{devices:JSON.stringify(data),userid:this.state.probe.UID},(result) => {
if (!result.err) return false;
console.log("Dongle already paired");
return true;
//logNetworkState
});
}
}
This is the Api.fetch function i wrote
fetch(action,data,cb){
let url=Config.URL+"?version="+Config.VERSION+"&action="+action;
let post="";
let formData=new FormData();
for(let k in data) formData.append(k,data[k]);
for(let k in data) post+="&"+k+"="+encodeURIComponent(data[k]).replace(/%20/g,'+');
console.log(url+post);
console.log(url);
if (data.batch) console.log(data.batch);
let sending=true;
fetch(url,{
method: 'post',
body: formData
})
.then(function(response){
if (true) return response.json();
let txt=response.text();
console.log(txt);
return JSON.parse(txt);
})
.then(
(result)=>{
if (!sending) return;
sending=false;
console.log(JSON.stringify(result));
if (cb) cb(result);
},
(error)=>{
if (!sending) return;
sending=false;
console.log("fetch error");
console.log(error);
if (cb) cb();
}
);
setTimeout(()=>{
console.log("http timeout")
if (!sending) return console.log("nothing to abort");
if (cb) cb();
},Config.HTTP_TIMEOUT*1000)
}
}
And this is my main code where I wait for the first function donglePaired, and if donglePaired return true I send an error to the user.
let donglePaired = await this.props.app.donglePaired();
if (donglePaired) return this.props.app.setError("ERR_DONGLE");
The problem is that the program doesnt wait for donglePaired, despite of the await
your code here is inappropriate
let donglePaired = await this.props.app.donglePaired();
if (donglePaired) return this.props.app.setError("ERR_DONGLE");
Async function cannot return value normally unless it is a Promise
See my simple demo below!
async function test() {
const result = await asyncRequest()
return result
}
function asyncRequest() {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve('success')
}, 2000)
})
}
test().then((data) => {
console.log(data)
})
The snippets should give you an idea how to await the callback
Sending to the API
async function remove_configuration(filename) {
const data = { filename };
const options = {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(data)
};
await fetch('/delete', options);
}
Just Retrieving Data
async function display() {
let response = await fetch('/get-available-configurations')
let data = await response.json(); // JSON or Text what do you prefer
// do something with data
}
You could return an Promise.race() with your timeout function.
fetch(action, data, cb) {
let url = Config.URL + "?version=" + Config.VERSION + "&action=" + action;
let post = "";
let formData = new FormData();
for (let k in data) formData.append(k, data[k]);
for (let k in data)
post += "&" + k + "=" + encodeURIComponent(data[k]).replace(/%20/g, "+");
console.log(url + post);
console.log(url);
if (data.batch) console.log(data.batch);
let sending = true;
return Promise.race([
fetch(url, {
method: "post",
body: formData
})
.then(res => res.json())
.then(result => {
if (!sending) return;
sending = false;
return result;
}),
sleep(Config.HTTP_TIMEOUT * 1000)
]);
}
const sleep = ms => new Promise((_, rej) => setTimeout(rej("TIMEOUT"), ms));
It either returns you the value or it rejects with TIMEOUT or it rejects with an error from fetch
And donglePaired looks like this then. I have wrapped it with an try / catch
async donglePaired() {
if (Platform.OS !== "ios") {
var pairedDevices = await BluetoothScanner.getPairedDevices();
console.log("Sending........");
let data = {
data: pairedDevices
};
try {
let result = await new Api().fetch("bluetoothCheck", {
devices: JSON.stringify(data),
userid: this.state.probe.UID
});
if (!result.err) return false;
console.log("Dongle already paired");
return true;
//logNetworkState
} catch (err) {
console.log(err);
}
}
}
One possibility is to drop the async and change it to this:
donglePaired() {
return new Promise( function(resolve, reject) {
if (Platform.OS !=='ios'){
var pairedDevices = await BluetoothScanner.getPairedDevices();
console.log('Sending........');
let data={
data:pairedDevices,
};
new Api().fetch("bluetoothCheck",{devices:JSON.stringify(data),userid:this.state.probe.UID},(result) => {
if (!result.err) reject(false);
console.log("Dongle already paired");
resolve(true);
//logNetworkState
});
}
reject(false);
});
}
And:
this.props.app.donglePaired().then( (response) => {
// do something here, this will only run if the response is true
});
I am unable to run the following code.
It shows me this error:
SyntaxError: await is only valid in async function
const Prom = async() => {
return new Promise((resolve, reject) => {
let a = 2;
if (a == 2) {
resolve('Its working');
} else {
reject('Its not working');
}
});
};
const final = await Prom();
console.log(final);
You could use IIFE
const Prom = async () => {
return new Promise((resolve, reject) => {
let a = 2
if (a == 2) {
resolve('Its working')
} else {
reject('Its not working')
}
})
}
;(async function() {
const final = await Prom()
console.log(final)
})()
const Prom = async () => {
return new Promise((resolve, reject) => {
let a = 2;
if (a == 2) {
resolve('Its working');
} else {
reject('Its not working');
}
});
};
const final = async () => {
const result = await Prom();
console.log(result);
};
final();
await can only be used inside an async function.
The error here is referring to the final variable. It has to be inside of an async function. Try using the below code.
const prom = new Promise((resolve, reject) => {
let a = 2;
if (a == 2) {
resolve('Its working');
} else {
reject('Its not working');
}
});
(async function() {
const final = await prom;
console.log(final)
})()