Develop Reference

How to intercept error on a Promise with async/await?

On a NodeJs project, I call my async function this way:
const response = await myFunction();
Here's the definition of the function:
myFunction = async () => {
return await new Promise((next, fail) => {
// ...
axios({
method: 'get',
url: apiEndpoint,
data: payload
}).then(function (response) {
// ...
next(orderId);
}).catch(function (error) {
fail(error);
});
});
}
How should I correctly intercept an error if that's happens? i.e. how I manage it when I await the function?
EDIT: as requested, a more complete snippet:
import express from 'express';
import { helpers } from '../helpers.js';
const router = express.Router();
router.post('/createOrder', helpers.restAuthorize, async (req, res) => {
// ...
const orderId = await api.createOrder();
let order = {
buyOrderId: orderId
}
const placed = await api.checkPlaced(orderId);
if (placed) {
let ack = await api.putAck(orderId);
order.checksum = placed.checksum;
order.ack = ack;
}
InternalOrder.create(order, (error, data) => {
if (error) {
return res.status(500).send({ message: error });
} else {
res.json("ok");
}
})
})
export { router as exchangeRouter }

Use try/catch:
let response;
try {
response = await myFunction();
} catch (error) {
// Handle error here.
}

URQL WSS connection with GraphQL-WS says error 4500

import {
createClient,
defaultExchanges,dedupExchange, cacheExchange, fetchExchange,
subscriptionExchange,
gql
} from "#urql/core";
import { createClient as createWSClient } from "graphql-ws";
import { pipe, subscribe } from "wonka";
import { getToken, setToken } from "./helper";
const wsClient = createWSClient({
url: 'wss://**********/subscriptions',
reconnect: true,
});
const client = createClient({
url: "https://***********/",
fetchOptions: () => {
const token = getToken()
return token ? { headers: { authorization: `Bearer "${token}"` } } : {}
},
// the default:
exchanges: [
...defaultExchanges,
subscriptionExchange({
forwardSubscription(operation) {
return {
subscribe: (sink) => {
const dispose = wsClient.subscribe(operation, sink);
return {
unsubscribe: dispose,
};
},
};
},
}),
]
});
SUB_TO_MESSAGES = async () => {
console.log('sub')
const token = getToken();
console.log(String(token))
const { unsubscribe } = pipe(
await client.subscription(messageAdded,{ jwt: token }),
subscribe((result) => {
console.log(result)
})
)
};
I dont get the same issue with try and catch using GraphQL-WS but I still dont get any data from the server. The assignment is a vanillaJS project using GraphQL.I didndt post the url, jwt token,or the GET, POST, REgG as they work as intended. The rendering is done with a proxy. The error message is:
Connection Closed: 4500 Cannot read properties of undefined (reading 'Authorization')
Even playground doesnt work. Something wrong with the endpoint. It worked 2 weeks ago but admin says it still work yet I can find the problem. It used to work for me.
Here is the try and catch version:
import { createClient} from "graphql-ws";
import pStore from "./handler.js";
import { getToken } from "./helper";
const client = createClient({
url: "wss://******/subscriptions",
reconnect: true,
connectionParams:{
headers: {
"Authorization":`Bearer ${getToken()}`
}
},
})
async SUB_MESSAGE() {
try {
console.log('called Gql server')
const onNext = (res) => {
let obj = res.data.messageAdded
console.log(obj)
pStore[obj.id] = obj
pStore.render(obj)
};
let unsubscribe = () => {
/* complete the subscription */
};
new Promise((resolve, reject) => {
client.subscribe({
query: `subscription{messageAdded(jwt:"${getToken()}"){id text fromAgent createdAt updatedAt}}`,
},
{
next: (data)=> onNext(data),
error: reject,
complete: () => resolve(true),
})
})
}catch(error){
console.error('There has been a problem with your ws operation:', error);
}
}
Either way I think its a ad character, scope issue but I dont know where.

Unsubscribe email using Fetch api Javascript

I have a form where i enter an email and it gets ''subscribed'' in a user.json file using a fetch api on node server.My task is to :
upon clicking on the "Unsubscribe" button, implement the functionality for unsubscribing from the community list. For that, make POST Ajax request using http://localhost:3000/unsubscribe endpoint.
I tried to make the function but it wasnt succeseful so i deleted it. Also,i need to do the following :
While the requests to http://localhost:3000/subscribe and
http://localhost:3000/unsubscribe endpoints are in progress, prevent
additional requests upon clicking on "Subscribe" and "Unsubscribe".
Also, disable them (use the disabled attribute) and style them using
opacity: 0.5.
For me ajax requests,fetch and javascript is something new,so i dont know really well how to do this task,if you could help me i'll be happy,thanks in advance.
fetch code for subscribing:
import { validateEmail } from './email-validator.js'
export const sendSubscribe = (emailInput) => {
const isValidEmail = validateEmail(emailInput)
if (isValidEmail === true) {
sendData(emailInput);
}
}
export const sendHttpRequest = (method, url, data) => {
return fetch(url, {
method: method,
body: JSON.stringify(data),
headers: data ? {
'Content-Type': 'application/json'
} : {}
}).then(response => {
if (response.status >= 400) {
return response.json().then(errResData => {
const error = new Error('Something went wrong!');
error.data = errResData;
throw error;
});
}
return response.json();
});
};
const sendData = (emailInput) => {
sendHttpRequest('POST', 'http://localhost:8080/subscribe', {
email: emailInput
}).then(responseData => {
return responseData
}).catch(err => {
console.log(err, err.data);
window.alert(err.data.error)
});
}
index.js from route node server:
const express = require('express');
const router = express.Router();
const FileStorage = require('../services/FileStorage');
/* POST /subscribe */
router.post('/subscribe', async function (req, res) {
try {
if (!req.body || !req.body.email) {
return res.status(400).json({ error: "Wrong payload" });
}
if (req.body.email === 'forbidden#gmail.com') {
return res.status(422).json({ error: "Email is already in use" });
}
const data = {email: req.body.email};
await FileStorage.writeFile('user.json', data);
await res.json({success: true})
} catch (e) {
console.log(e);
res.status(500).send('Internal error');
}
});
/* GET /unsubscribe */
router.post('/unsubscribe ', async function (req, res) {
try {
await FileStorage.deleteFile('user.json');
await FileStorage.writeFile('user-analytics.json', []);
await FileStorage.writeFile('performance-analytics.json', []);
await res.json({success: true})
} catch (e) {
console.log(e);
res.status(500).send('Internal error');
}
});
module.exports = router;
And user.json file looks like this :
{"email":"Email#gmail.com"}
This is my attempt for unsubscribing :
export const unsubscribeUser = () => {
try {
const response = fetch('http://localhost:8080/unsubscribe', {
method: "POST"
});
if (!response.ok) {
const message = 'Error with Status Code: ' + response.status;
throw new Error(message);
}
const data = response.json();
console.log(data);
} catch (error) {
console.log('Error: ' + error);
}
}
It gives the following errors:
Error: Error: Error with Status Code: undefined
main.js:2
main.js:2 POST http://localhost:8080/unsubscribe 404 (Not Found)
FileStorage.js:
const fs = require('fs');
const fsp = fs.promises;
class FileStorage {
static getRealPath(path) {
return `${global.appRoot}/storage/${path}`
}
static async checkFileExist(path, mode = fs.constants.F_OK) {
try {
await fsp.access(FileStorage.getRealPath(path), mode);
return true
} catch (e) {
return false
}
}
static async readFile(path) {
if (await FileStorage.checkFileExist(path)) {
return await fsp.readFile(FileStorage.getRealPath(path), 'utf-8');
} else {
throw new Error('File read error');
}
}
static async readJsonFile(path) {
const rawJson = await FileStorage.readFile(path);
try {
return JSON.parse(rawJson);
} catch (e) {
return {error: 'Non valid JSON in file content'};
}
}
static async writeFile(path, content) {
const preparedContent = typeof content !== 'string' && typeof content === 'object' ? JSON.stringify(content) : content;
return await fsp.writeFile(FileStorage.getRealPath(path), preparedContent);
}
static async deleteFile(path) {
if (!await FileStorage.checkFileExist(path, fs.constants.F_OK | fs.constants.W_OK)) {
return await fsp.unlink(FileStorage.getRealPath(path));
}
return true;
}
}
module.exports = FileStorage;

You should consider using a database for handling CRUD operations on your persisted data. If you must use filestorage, theres a flat file DB library called lowdb that can make working the files easier.
As for preventing duplicate requests, you can track if user has already made a request.
let fetchBtn = document.getElementById('fetch')
let isFetching = false
fetchBtn.addEventListener('click', handleClick)
async function handleClick(){
if (isFetching) return // do nothing if request already made
isFetching = true
disableBtn()
const response = await fetchMock()
isFetching = false
enableBtn()
}
function fetchMock(){
// const response = await fetch("https://example.com");
return new Promise(resolve => setTimeout (() => resolve('hello'), 2000))
}
function disableBtn(){
fetchBtn.setAttribute('disabled', 'disabled');
fetchBtn.style.opacity = "0.5"
}
function enableBtn(){
fetchBtn.removeAttribute('disabled');
fetchBtn.style.opacity = "1"
}
<button type="button" id="fetch">Fetch</button>

Handling query in React and Express

Somewhere in my React application I used REST API to send request to the server. In my URL I want to use query (in the postIconsTransition method), but when I send a request to the server, server tells me could not found this URL (I build this error in my server). If I use this URL without any query the request in the postIconsTransition method works fine. postId and authContext.userId work fine, can anyone tell me what's wrong with my code?
In my component where I send request:
const likeHandler = async () => {
setLike(prevState => !prevState);
if (!like) {
try {
await postIconsTransition(props.postId, "inc");
} catch (error) {}
} else {
try {
await postIconsTransition(props.postId, "dec");
} catch (error) {}
}
};
In useHttp.js component:
const postIconsTransition = async (postId, addtionAddress) => {
return await transitionData(
`http://localhost:5000/post/${postId}/${authContext.userId}?t=${addtionAddress}`,
"POST",
null,
{ Authorization: `Bearer ${authContext.token}` }
);
};
transitionData method:
const transitionData = useCallback(
async (url, method = "GET", body = null, headers = {}) => {
setIsLoading(true);
const abortController = new AbortController();
activeHttpRequest.current.push(abortController);
try {
const response = await fetch(url, {
method,
body,
headers,
signal: abortController.signal
});
const responseData = await response.json();
activeHttpRequest.current = activeHttpRequest.current.filter(
reqCtrl => reqCtrl !== abortController
);
if (!response.ok) {
throw new Error(responseData.message);
}
setIsLoading(false);
return responseData;
} catch (error) {
modalContext.err(error);
setIsLoading(false);
throw error;
}
},
[modalContext.err]
);
In Express:
router.post(
"/:postId/:userId?t=inc",
tokenChecker,
postController.updateLikesComments
);
router.post(
"/:postId/:userId?t=dec",
tokenChecker,
postController.updateLikesComments
);
All of them work fine but when I use query in my URL, it's not working any more.

You don't specify query parameters in express routes like that. Just send them. Express can read it.
router.post(
"/:postId/:userId",
tokenChecker,
postController.updateLikesComments
);
// Notice that you don't need the other one.
and in your controller check the parameter
// controller's code
const t = req.query.t;
if (t === 'inc') {
// do what you want here
}
if (t === 'dec') {
// do what you want here
}

Service call is not going in react-native. Getting warning like "Possible unhandled Promise Rejection, Reference error: response is not defined"

I am new to react native and making service call for the first time. My problem is service call is not going and getting warning like
Possible unhandled Promise Rejection, Reference error: response is not defined.
I am trying to hit loginUser function.
Api.js
const BASE_URL = "http://localhost:8200";
export const api = async (url, method, body = null, headers = {}) => {
try {
const endPoint = BASE_URL.concat(url);
const reqBody = body ? JSON.stringify(body) : null;
const fetchParams = {method, headers};
if((method === "POST" || method === "PUT") && !reqBody) {
throw new Error("Request body required");
}
if(reqBody) {
console.log("ReQBody--->"+reqBody);
fetchParams.headers["Content-type"] = "application/json";
fetchParams.body = reqBody;
}
const fetchPromise = await fetch(endPoint, fetchParams);
const timeOutPromise = new Promise((resolve, reject) => {
setTimeout(() => {
reject("Request Timeout");
}, 3000);
});
const response = await Promise.race([fetchPromise, timeOutPromise]);
return response;
} catch (e) {
return e;
}
}
export const fetchApi = async (url, method, body, statusCode, token = null, loader = false) => {
console.log("In FetchAPi Function");
try {
const headers = {}
const result = {
token: null,
success: false,
responseBody: null
};
if(token) {
headers["securityKey"] = token;
}
const response = await api(url, method, body, headers);
console.log("fetchApi-->>"+response);
if(response.status === statusCode) {
result.success = true;
let responseBody;
const responseText = await response.text();
try {
responseBody = JSON.parse(responseText);
} catch (e) {
responseBody = responseText;
}
result.responseBody = responseBody;
return result;
}
let errorBody;
const errorText = await response.text();
try {
errorBody = JSON.parse(errorText);
} catch (e) {
errorBody = errorText;
}
result.responseBody = errorBody;
console.log("FetchApi(Result)--->>"+result);
throw result;
} catch (error) {
return error;
}
}
auth.actions.js
export const loginUser = (payload) => {
console.log("In LoginUser function2");
return async (dispatch) => {
<-----**I am not able to enter into this block**------>
try {
dispatch({
type: "LOGIN_USER_LOADING"
});
console.log("In LoginUser function3");
const response = await fetchApi("/login", "POST", payload, 200);
if(response.success) {
dispatch({
type: "LOGIN_USER_SUCCESS",
});
dispatch({
type: "AUTH_USER_SUCCESS",
token: response.token
});
dispatch({
type: "GET_USER_SUCCESS",
payload: response.responseBody
});
return response;
} else {
throw response;
}
} catch (error) {
dispatch({
type: "LOGIN_USER_FAIL",
payload: error.responseBody
});
return error;
}
}
}
In console log, I can't see anything in network tab. In the android emulator, the mentioned warning has come.
My console tab

I see that your BASE_URL is served using an http endpoint. You can only make requests to https endpoints from react native projects. A possible workaround is to use ngrok. Just download it and run ./ngrok http 8200 since your port number is 8200. It will expose an HTTPS endpoint and replace your BASE_URL with that link and try fetching the data again.

I use the following code to make API calls. See if you can integrate it in your code. it is quite simple:
In a class called FetchService:
class FetchService {
adminAuth(cb, data) {
console.log('here in the fetch service');
return fetch(
baseURL + "login",
{
method: "POST",
headers: {
Accept: "application/json",
},
body: data
}
)
.then((response) => response.json())
.then(responsej => {
cb(null, responsej);
})
.catch(error => {
cb(error, null);
});
}
}
export default FetchService;
Then call it from your component using:
import FetchService from './FetchService';
const fetcher = new FetchService;
export default class LoginScreen extends React.Component {
fetchData() {
const data = new FormData();
data.append('username',this.state.username);
data.append('password',this.state.password);
fetcher.wastereport((err, responsej) => {
if(err) {
//handle error here
} else {
//handle response here
}
}, data);
}
}