I have the following files:
My routes - where the orders_count route lives:
routes/index.js
const express = require('express');
const router = express.Router();
const transactionsController = require('../controllers/transactionsController');
const ordersController = require('../controllers/ordersController');
const ordersCountController = require('../controllers/ordersCountController');
router.get('/transactions', transactionsController);
router.get('/orders', ordersController);
router.get('/orders_count', ordersCountController);
module.exports = router;
I then have my orders count controller living in the controllers directory:
controllers/ordersCountController.js
const ordersCountService = require('../services/ordersCountService');
const ordersCountController = (req, res) => {
ordersCountService((error, data) => {
if (error) {
return res.send({ error });
}
res.send({ data })
});
};
module.exports = ordersCountController;
My controller then calls my order count service which fetches data from another API.
services/ordersService.js
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = (req, res) => {
const url = ...;
const settings = { method: 'Get'};
fetch(url, settings)
.then(res => {
if (res.ok) {
res.json().then((data) => {
return data;
});
} else {
throw 'Unable to retrieve data';
}
}).catch(error => {
console.log(error);
});
}
module.exports = ordersCountService;
I'm trying to return the JSON response. I initially had it setup with requests but looking at the NPM site, it appears that it's depreciated so have been digging through how to use node-fetch.
I have tried both 'return data' and res.send({data}), but neither are solving the problem.
I am still new to this so I am likely missing something very obvious, but how come I am not sending the JSON back through so that it displays at the /api/orders_count endpoint?
I keep thinking I messed something up in my controller but have been looking at it for so long and can't seem to figure it out.
Any help would be greatly appreciated and if there is anything I can add for clarity, please don't hesitate to ask.
Best.
please learn promises and await syntax. life will be easier.
never throw a string. always prefer a real error object, like that : throw new Error('xxx'); that way you will always get a stack. its way easier to debug.
avoid the callback hell : http://callbackhell.com/
you need to decide if you want to catch the error in the controller or in the service. no need to do in both.
in the controller you call the service that way :
ordersCountService((error, data) => {
but you declare it like that :
const ordersCountService = (req, res) => {
which is not compatible. it should look like this if you work with callback style :
const ordersCountService = (callback) => {
...
if (error) return callback(error)
...
callback(null, gooddata);
here is an example to flatten your ordersCountService function to await syntax, which allows the "return data" you were trying to do :
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = async (req, res) => {
const url = ...;
const settings = { method: 'Get'};
try {
const res = await fetch(url, settings);
if (!res.ok) throw new Error('Unable to retrieve data');
return await res.json();
} catch(error) {
console.log(error);
}
}
module.exports = ordersCountService;
in fact i would prefer to error handle in the controller. then this woud be sufficient as a service
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = async () => {
const url = ...;
const settings = { method: 'Get'};
const res = await fetch(url, settings);
if (!res.ok) throw new Error('Unable to retrieve data');
return await res.json();
}
module.exports = ordersCountService;
then you can call this funtion like this :
try {
const data = await ordersCountService(req, res);
} catch(err) {
console.log(err);
}
//or
ordersCountService(req, res).then((data) => console.log(data)).catch((err) => console.error(err));
Related
My self and another developer are working on an API using node.js and we are not advanced coders yet. We ran into problem. I will try and explain the problem here with sample references.
We have an API route that would be called on the frontend, please this is just a sample and not the real code. client said the codes should be private. We want to stop the function when an error is detected in another function we called. I am sure that we are not doing it rightly. Here is the API route for this post request and we called another function that we exported and imported here.
We simply want the httpCreateHarsh function to end if there is an error in the anotherFunction. With what we have, the error is seen in console.log when the user is not an admin for example but the httpCreateHarshfunction keeps running until it reaches the last line. Is this possible? Or is there another way we can structure the code to achieve this?
Shared sample of my code
const callAnotherFunction = require("../anotherfunction")
const httpCreateHarsh = async(req, res) => {
await callAnotherFunction(req, res);
return res.status(200).json('created')
}
//This is the second function we called:
const obj = {
status: 'success',
code: '244'
}
const anotherFunction = async(req, res) => {
if (req.body.user !== 'admin') {
return res.status(401).json('Unauthorized')
}
return obj
}
export default = anotherFunction
//The route here:
const express = require('express');
const router = express.Router();
const httpCreateHarsh = require('../httpCreateHarsh');
router.post("/harsh", httpCreateHarsh)
You couldn't return the res object in your second function.
To solve this problem you could throw exceptions and catch them in your handler function.
// request handler function
const httpCreateHarsh = async (req, res) => {
try {
await callAnotherFunction(req, res);
} catch (e) {
return res.status(401).json('Unauthorized')
}
return res.status(200).json('created')
}
const anotherFunction = asyn(req, res) => {
if (req.body.user !== 'admin') {
throw new Error('Unauthorized')
}
return obj
}
What you can do is you can wrap the code in httpCreateHarsh in an try...catch so whenever there is error inside it it will trigger the catch block and u exit the api.
const httpCreateHarsh = async(req, res)=>{
try{
await callAnotherFunction(req, res);
return res.status(200).json('created')
} catch(err){
return res.status(401).json('Unauthorized')
}
}
As an addition to this code you can return a promise from anotherFunction so that the catch block will be triggered once the promise is rejected.
For Exmaple:
const anotherFunction = async(req, res) => {
return new Promise(function(myResolve, myReject) {
if (req.body.user !== 'admin') {
myReject();
}
myResolve(obj);
});
}
If the code runs as you want it, it will generate the "cannot set headers after they are sent to the client" error, because you will be returning 2 responses
the first will be "unauthorized" by "anotherFunction" function and then the other response which is "created" of the current function "httpCreateHarsh".
what you should do instead is to call the "anotherFunction" as a middleware before moving to the "httpCreateHarsh" function.
it can be done this way:
// anotherfunction.js file containing the function you want to import
module.exports = {
async anotherFunction(req, res) {
if (req.body.user !== 'admin') {
return res.status(401).json('Unauthorized')
}
// this way, you can access this object from the "httpCreateHarsh" function by using req.body.obj
req.body.obj = {
status: 'success',
code: '244'
}
// this next indicates that there were no errors, and the next function will be called
next();
}
}
const httpCreateHarsh = async(req, res) => {
// do wathever you want here
return res.status(200).json('created')
}
//The route here:
const express = require('express');
const router = express.Router();
const httpCreateHarsh = require('../httpCreateHarsh');
const callAnotherFunction = require("../anotherfunction")
router.post("/harsh", (req, res, next) => callAnotherFunction(req, res, next), httpCreateHarsh)
I want to separate controllers and services in my Express app, currently, I have a service that generates an XLSX file using ExcelJS, I want to reuse the service so, I don't want to pass the response object to the service, is there a way I can return the file from the service to the controller?
Right now I have the following
const generateXLSX = (res, data) => {
let baseFile = "path/to/template.xlsx";
let wb = new Excel.Workbook();
wb.xlsx
.readFile(baseFile)
.then(async () => {
// add data to template
}
await wb.xlsx.write(res);
res.end();
})
.catch((err) => {
console.log(err);
res.status(500);
});
};
In this function I'm using the response object in the service, I want to know if there's a way to return the file without using write(res), and send it in the controller
Your generateXLSX function could return a "pass-through" readable stream which you then pipe into the res object. Something like
const {PassThrough} = require("stream");
function generateXLSX(data) {
let baseFile = "path/to/template.xlsx";
let wb = new Excel.Workbook();
let readable = new PassThrough();
wb.xlsx
.readFile(baseFile)
.then(async function() {
// add data to template
await wb.xlsx.write(readable);
readable.end();
})
.catch((err) => {
readable.destroy(err);
});
return readable;
}
app.use("/path", function(req, res) {
generateXLSX(req.query.data).pipe(res);
});
I would like to create a local Javascript module I can "require" in other files to handle all MongoDB CRUD operations.
I wrote something as:
-- dbConn.js file --
require('dotenv').config()
const MongoClient = require('mongodb').MongoClient
const ObjectID = require('mongodb').ObjectID
let _connection
const connectDB = async () => {
try {
const client = await MongoClient.connect(process.env.MONGO_DB_URI, {
useNewUrlParser: true,
useUnifiedTopology: true
})
console.log('Connected to MongoDB')
return client
} catch (err) {
console.log(error)
}
}
exports.findOne = async () => {
let client = await connectDB()
if (!client) {
return;
}
try {
const db = client.db("Test_DB");
const collection = db.collection('IoT_data_Coll');
const query = {}
let res = await collection.findOne(query);
return res;
} catch (err) {
console.log(err);
} finally {
client.close();
}
}
exports.findAll = async () => {
let client = await connectDB()
if (!client) {
return;
}
try {
const db = client.db("Test_DB");
const collection = db.collection('IoT_data_Coll');
const query = {}
let res = await collection.find(query).toArray();
return res;
} catch (err) {
console.log(err);
} finally {
client.close();
}
}
Then in another file (not necessary inside Express app), say
-- app.js ---
const findAll = require('./dbConn').findAll
const findOne = require('./dbConn').findOne
findAll().then(res => JSON.stringify(console.log(res)))
findOne().then(res => JSON.stringify(console.log(res)))
I wonder if it is correct?
I have to close the connection after each method/CRUD operation?
I was trying to use IIF instead of ".then", as:
(async () => {
console.log(await findOne())
})()
But I receive a weird error saying that findAll is not a function.
What's wrong with it?
Thanks.
It really depends on your use case which isn’t clear If you are using Express or just stand alone and how frequent are you planning to run app.js
Either way your code is expensive, each time you reference dbCon.js you are opening a new connection to the database.
So you can fix app.js by only requiring dbCon.js once and use it..
The best practice is to ofcourse use connection pooling https://www.compose.com/articles/connection-pooling-with-mongodb/
I am building a simple application for my portfolio using The Movie Database api. In my GET /movie route, I want to get and display the data about the movie, and the names and photos of the cast members, however the data for the movie and the data for the cast members belong two separate endpoints of the api, and I am at a complete loss as to how to access both response data sets under a single endpoint in my app.
I cannot call axios.get() on both endpoints under the /movie route because I will get a "Headers already sent" error, and I have tried to write a function that uses axios.get for 1 endpoint that returns the response and gets called in my GET /movie route, but that causes the entire GET route to return undefined.
Here is my current code for my /movie route that is incorrect, but closely conveys what I am trying to accomplish
const express = require('express');
const router = express.Router();
const axios = require('axios');
const api_key = require('../config/keys').api_key;
const imgURL = "http://image.tmdb.org/t/p/";
const dateFormat = require('../config/dateFormat');
getActors = movie_id => {
axios.get(`https://api.themoviedb.org/3/movie/${movie_id}/credits?api_key=${api_key}&language=en-US`)
.then(res => {
return res.data;
}).catch(err => console.log(err.message));
}
router.get('/:id', (req, res) => {
const id = req.params.id
axios.get(`https://api.themoviedb.org/3/movie/${id}?api_key=${api_key}&language=en-US`)
.then(res => {
const movieData = res.data;
const actors = getActors(id); //calling above function here, but returns undefined and hangs the application
res.render('movie', {movieInfo: movieData, imgURL: imgURL, releaseDate: dateFormat(movieData.release_date), actors: actors})
})
.catch(err => console.log(err.status_message))
});
module.exports = router;
any help is greatly appreciated.
You can use axios.all to concatenate several promises and executing them in parallel. Then, once all the added requests have been finished, you can handle with the then promise the result of all of them. For instance, in your code:
const express = require('express');
const router = express.Router();
const axios = require('axios');
const api_key = require('../config/keys').api_key;
const imgURL = "http://image.tmdb.org/t/p/";
const dateFormat = require('../config/dateFormat');
axios.all([
axios.get(`https://api.themoviedb.org/3/movie/${movie_id}/credits?api_key=${api_key}&language=en-US`),
axios.get(`https://api.themoviedb.org/3/movie/${id}?api_key=${api_key}&language=en-US`)
])
.then(axios.spread((actorsRes, moviesRes) => {
// Your logic with each response
});
module.exports = router;
I see that getActors is currently returning null. Change it to...
const getActors = movie_id => {
return axios.get(`https://api.themoviedb.org/3/movie/${movie_id}/credits?api_key=${api_key}&language=en-US`)
.then(res => {
return res.data;
}).catch(err => console.log(err.message));
}
Another problem is calling of getActors function. It's a function that contains asynchronous function axios.get(). Change that to ..
router.get('/:id', (req, res) => {
let movieData;
const id = req.params.id
axios.get(`https://api.themoviedb.org/3/movie/${id}?api_key=${api_key}&language=en-US`)
.then(res => {
movieData = res.data;
return getActors(id);
})
.then(actors => {
res.render('movie', {movieInfo: movieData, imgURL: imgURL, releaseDate: dateFormat(movieData.release_date), actors: actors})
})
.catch(err => console.log(err.status_message))
});
I have another app which uses express and routes but this new app i was slimming it down. I know the connection string stuff is correct
script.getQuestions(connection);
script.getQuestions = function(connection,req, res){
console.log(connection);
}
I have read that some people said online to change to use a promise for async fixes this... problem is that with my function having req and res i don't know how to pass those in when i even try to refactor with a promise
"ConnectionError: Connection is closed"
"(module.js:487:32) code: 'ECONNCLOSED', name: 'ConnectionError' }"
What I call up (script) is
var sql = require('mssql');
exports.getQuestions = function(connection, req,res){
console.log(connection);
var request = new sql.Request(connection);
var query = 'select * from Question'
request.query(query).then(function(resultset){
res.json(resultset.recordset);
}).catch(function(err){
console.log(err);
//res.json(err)
})
}
it's a bit hard to understand what you're doing there. But here is an promise example to use mssql
const sql = require('mssql')
sql.connect(config).then(pool => {
// Query
return pool.request()
.input('input_parameter', sql.Int, value)
.query('select * from mytable where id = #input_parameter')
}).then(result => {
console.dir(result)
// Stored procedure
return pool.request()
.input('input_parameter', sql.Int, value)
.output('output_parameter', sql.VarChar(50))
.execute('procedure_name')
}).then(result => {
console.dir(result)
}).catch(err => {
// ... error checks
})
sql.on('error', err => {
// ... error handler
})
source: https://www.npmjs.com/package/mssql#promises