Develop Reference

Problem while fetching a route from another route

I have a route to check if a user is logged in. It works well, but I don't understand what is the problem if I create a second route just below that calls it just to do the same thing. It seems like I can't access the cookie anymore in the second route, but I don't know why. Thanks for your help !
// This route works :
router.get('/loggedin', async (req, res) => {
try {
const token = req.cookies.jwt;
console.log("token : " + token) // Token is correct here in loggedin route, but is undefined if I use the route below
const decodedToken = jwt.verify(token, process.env.JWT_SECRET);
if (decodedToken) {
res.send(true);
}
else {
res.send(false);
}
}
catch (err) {
res.status(500).send(false);
}
});
// This route calls the route above and doesn't work
router.get('/loggedinbyanotherway', async (req, res) => {
const checking = await fetch(`${process.env.API_URL}:${process.env.PORT || 3000}/loggedin`)
console.log(checking.ok) // Returns false
const data = await checking.json()
console.log(data) // Returns false
res.send(data)
});

Your fetch request isn't providing any cookies, so how could the code handling the request read any cookies?
More to the point... This entire operation is unnecessary. Why make an HTTP request to the application you're already using? Instead, extract the functionality you want into a common function and just call that function from both routes. For example:
const isLoggedIn = (req) => {
const token = req.cookies.jwt;
const decodedToken = jwt.verify(token, process.env.JWT_SECRET);
if (decodedToken) {
return true;
} else {
return false;
}
};
router.get('/loggedin', async (req, res) => {
try {
res.send(isLoggedIn(req));
}
catch (err) {
res.status(500).send(false);
}
});
router.get('/loggedinbyanotherway', async (req, res) => {
const checking = isLoggedIn(req);
res.send(checking);
});
In the example it's not really clear why you need the second route or what else it offers, but I can only assume it's just a placeholder for some additional functionality you plan to add.
Either way, the point is that the application doesn't need to make an entire HTTP request to itself, since you're already in that application and have access to the same logic.

How to get a variable from front to a service worker?

Some context
I've created a service worker to send notifications to registered users.
It works well until I tried to implement a sort of id to each people who register to a service worker (to send notification).
I do that because I have to delete old registration from my database, so I took the choice to let each users three registration (one for mobile device and two others for different navigator on computer) and if there is more, I want to remove from the database the older.
Tools
I'm using nodejs, express and mySql for the database.
The issue
When I launch a subscription I got this error:
SyntaxError: Unexpected token o in JSON at position 1
at JSON.parse (<anonymous>)
I saw in an other post that it's because they try to JSON.parse what's already an object.
But in my case, I can't find where I parse, see the part which are concerned:
// service.js (service worker file)
// saveSubscription saves the subscription to the backend
const saveSubscription = async (subscription, usrCode) => {
const SERVER_URL = 'https://mywebsite:4000/save-subscription'
subscription = JSON.stringify(subscription);
console.log(subscription); // I got here what I expect
console.log(usrCode); // <-------------------------------- HERE I GOT UNDEFIND
const response = await fetch(SERVER_URL, {
method: 'post',
headers: {
'Content-Type' : 'application/json',
},
body : {
subscription: subscription,
usrCode: usrCode
}
})
return response
}
But when I console.log(usrCode) in my inspector, I got the good value.
So how should I do to get the value in service.js
Maybe the problem is from:
const bodyParser = require('body-parser')
app.use(bodyParser.json())
At the beginning I thought that the issue is from the back (because I'm not really good with async function).
And here is the back, If maybe I got something wrong.
// index.js (backend)
// Insert into database
const saveToDatabase = async (subscription, usrCode) => {
// make to connection to the database.
pool.getConnection(function (err, connection) {
if (err) throw err; // not connected!
console.log(usrCode);
console.log(subscription);
connection.query(`INSERT INTO webpushsub (webpushsub_info, webpushsub_code) VALUES ('${subscription}', '${usrCode}')`, function (err, result, fields) {
// if any error while executing above query, throw error
if (err) throw err;
// if there is no error, you have the result
console.log(result);
connection.release();
});
});
}
// The new /save-subscription endpoint
app.post('/save-subscription', async (req, res) => {
const usrCode = req.body.usrCode; // <------------------ I'm not sure about this part
const subscription = req.body.subscription
await saveToDatabase(JSON.stringify(subscription, usrCode)) //Method to save the subscription to Database
res.json({ message: 'success' })
})

By searching on google, I've found this tutorial. So the reason why usrCode is undefined is because the service worker doesn't have access to a data stored in front.
First you have to pass it in the URL as following:
// swinstaller.js (front)
// SERVICE WORKER INITIALIZATION
const registerServiceWorker = async (usrCode) => {
const swRegistration = await navigator.serviceWorker.register('service.js?config=' + usrCode); //notice the file name
return swRegistration;
}
And then get it in the service worker:
// service.js (service worker file)
// get the usrCode
const usrCode = new URL(location).searchParams.get('config');

For fetching a students applied programs

I am trying to fetch all the programs for the current applicant who is logged in and has applied for their bachelor's degree and store the fetched programs object id in an array.
I have tried the following but I'm not sure if it will work at first. Secondly, it will be quite helpful if you let me know what should I do to make it possible. I have shared the code I wrote. It is a MERN stack project and the backend is purely javascript.
Let me know if you can help me with the code below:
// #route GET /api/programs/applied-programs
// #desc Get all applied programs
// #access Private
router.get('/applied-programs', auth, async (req, res) => {
try {
const applicant = await Applicant.findOne({ user: req.user.id })
.select('-password')
.populate('user', ['email']);
let res = [];
const appliedPrograms = applicant.appliedPrograms.forEach(program => {
if (program) {
res = [program.id];
}
return res;
});
res.json(appliedPrograms);
} catch (err) {
console.log(err.message);
return res.status(500).send('Server Error');
}
});

So I just solved it myself. Just remembered that .forEach() function you have to pass an object the condition I was using was putting a check on the programs and I was passing the ids inside the array itself. Which surely is the wrong way to do it. So for now by using the .map() and mapping through the list of object and fetching their ids I just got what I wanted.
This is the proper way of doing so.
// #route GET /api/programs/applied-programs
// #desc Get all applied programs
// #access Private
router.get('/applied-programs/:id', auth, async (req, res) => {
try {
const applicant = await Applicant.findOne({ user: req.user.id })
.select('-password')
.populate('user', ['email']);
let response = [];
const appliedPrograms = applicant.appliedPrograms.map(
program => program.id
// if (program) {
// response = [program.id];
// }
// return response;
// }
);
response = appliedPrograms;
res.json(response);
} catch (err) {
console.log(err.message);
return res.status(500).send('Server Error');
}
});

Can't use #Res() with FilesInterceptor()

I am trying to upload a file using builtin multer and after then sending the response back to the user for success or failure. It was all going good until today, when I try to upload the Response wont come. after digging a bit I find out that when i use #res with #UploadedFile it does not execute the controller. I am new to nest.js.
Working.
#Post('uploads/avatar')
async uploadFile(#Req() req, #UploadedFile() avatar) {
console.log(req.body);
if (!req.body.user_id) {
throw new Error('id params not found.');
}
try {
const resultUpload = await this.userService.uploadUserImage(
req.body.user_id,
avatar,
); // returns the url for the uploaded image
return resultUpload;
} catch (error) {
console.log(error);
return error;
}
}
Not Working.
#Post('uploads/avatar')
async uploadFile(#Req() req, #UploadedFile() avatar, #Res() res) {
console.log(req.body);
if (!req.body.user_id) {
throw new Error('id params not found.');
}
try {
const resultUpload = await this.userService.uploadUserImage(
req.body.user_id,
avatar,
); // returns the url for the uploaded image
return resultUpload;
res.send(resultUpload);
} catch (error) {
console.log(error);
res.send(error);
}
}

In nest, you should always avoid injecting #Res because then you lose a lot of things that make nest so great: interceptors, exception filters,...
And actually, in most cases you don't need #Res since nest will automatically handle sending the response correctly.
If you want to send data from a controller method, you can just return the data (Promises and Observables will be resolved automatically as well). If you want to send an error to the client, you can just throw the corresponding HttpException, e.g. 404 -> NotFoundException:
#Post('uploads/avatar')
async uploadFile(#Req() req, #UploadedFile() avatar) {
if (!req.body.user_id) {
// throw a 400
throw new BadRequestException('id params not found.');
}
try {
const resultUpload = await this.userService.uploadUserImage(
req.body.user_id,
avatar,
);
return resultUpload;
} catch (error) {
if (error.code === 'image_already_exists') {
// throw a 409
throw new ConflictException('image has already been uploaded');
} else {
// throw a 500
throw new InternalServerException();
}
}
}
If for some reason you have to inject #Res here, you cannot use the FilesInterceptor. Then you have to configure the multer middleware yourself.
Side note
You can create a custom decorator for accessing the userId:
import { createParamDecorator } from '#nestjs/common';
export const UserId = createParamDecorator((data, req) => {
if (!req.body || !req.body.user_id) {
throw new BadRequestException('No user id given.')
}
return req.body.user_id;
});
and then use it in your controller method like this:
#Post('uploads/avatar')
async uploadFile(#UserId() userId, #UploadedFile() avatar) {

look, when you are using an interceptor, you are handling (with using .handle()) the stream of response (observable) not a whole package of it, but using express #Res actually is somehow getting around the whole flow of response streaming.
this is also explicitly mentioned in nestjs official documents:
We already know that handle() returns an Observable. The stream
contains the value returned from the route handler, and thus we can
easily mutate it using RxJS's map() operator.
WARNING
The response mapping feature doesn't work with the
library-specific response strategy (using the #Res() object directly
is forbidden).

how to break logic into a controller and a model in a node

I do not quite understand how to properly break the logic on the controllers and models in nodeJS when working with the backend application. Suppose I have an example
This code is in the model of my application, and logically I understand that the model is only responsible for choosing from the database, and the controller and everything else should be done by the controller, but I don’t quite understand how to do this and I tried to transfer part of the code to the controller and export it, but I did not succeed (Please, help, at least with this example! The main thing for me is to understand the principle of working with MVC in the node !!!
exports.currentPostPage = function(req, res){
db.query('SELECT * FROM `posts`', function (err, result) {
if (err){
console.log(err);
}
var post = result.filter(item => {return (item.id == req.params.id)? item: false})[0];
if (post === undefined){
res.render('pages/404');
} else {
res.render('pages/post-page', {postId: req.params.id, item: post});
}
});
};

So, you're on the right track. There's a lot of different ways to do it depending on preferences, but one pattern I've seen pretty commonly is to use the callback as a way to integrate. For example, let's say you have your model file:
exports.getPostById = (id, cb) => {
db.query('SELECT * FROM `posts` WHERE id=?', [id], function (err, result) {
if (err){
return cb(err); // or, alternatively, wrap this error in a custom error
}
// here, your logic is just returning whatever was returned
return cb(null, result);
});
};
Note I also am letting the DB handling the ID lookup, as it's probably more efficient at doing so for larger data sets. You didn't say what DB module you're using, but all the good ones have some way of doing parametrized queries, so use whatever works w/ your DB driver.
Anyway, the Model file therefore handles just the data interaction, the controller then handles the web interaction:
// postController.js
const model = require('../models/postModel.js'); // or whatever you named it
exports.populatePost = (req, res, next, id) => {
model.getPostById(id, (err, post) => {
if (err) return next(err); // centralized error handler
req.post = post;
next();
});
}
export.getOnePost = (req, res, next) => {
if (req.post) {
return res.render('pages/post-page', req.post);
}
// again, central error handling
return next({ status: 404, message: 'Post not found' });
}
I have mentioned central error handling; I vastly prefer it to scattering error handling logic all over the place. So I either make custom errors to represent stuff, or just do like above where I attach the status and message to an anonymous object. Either will work for our purposes. Then, in a middleware file you can have one or more handler, the simplest like this:
// middleware/errors.js
module.exports = (err, req, res, next) => {
console.error(err); // log it
if (err.status) {
return res.status(err.status).render(`errors/${err.status}`, err.message);
}
return res.status(500).render('errors/500', err.message);
}
Finally, in your routing setup you can do things like this:
const postController = require('../controllers/postController');
const errorHandler = require('../middleware/errors.js');
const postRouter = express.Router();
postRouter.param('postId', postController.populatePost);
postRouter.get('/:postId', postController.getOnePost);
// other methods and routes
app.use('/posts', postRouter)
// later
app.use(errorHandler);
As was pointed out in the comments, some folks prefer using the Promise syntax to callbacks. I don't personally find them that much cleaner, unless you also use the async/await syntax. As an example, if your db library supports promises, you can change the model code to look like so:
exports.getPostById = async (id, cb) => {
// again, this assumes db.query returns a Promise
return await db.query('SELECT * FROM `posts` WHERE id=?', [id]);
}
Then your controller code would likewise need to change to handle that as well:
// postController.js
const model = require('../models/postModel.js'); // or whatever you named it
exports.populatePost = async (req, res, next, id) => {
try {
const post = await model.getPostById(id)
req.post = post
return next()
} catch (err) {
return next(err)
}
}