I have a NEDB Datastore called users which contains one line of information. I call a fetch request to retrieve the users from the server and I can tell that the request is being processed by debugging. However, the users.find() is not working and I have no idea why. When I tried the same code with an alternate datastore, it worked fine.
Here is my Javascript code:
//Client side JS
async function extractUsers() {
const userJ = await fetch('/getUser');
let user = await userJ.json();
header.innerHTML = "Welcome " + user + "!";
}
//Server Side JS
const users = new Datastore('users.db');
users.loadDatabase();
app.get('/getUser', (req, res) => {
users.find({}, (err, data) => {
res.json(data);
})
});
If you have any idea why this is happening or need more information, please let me know. Thanks!
I simply deleted the users.db file and restarted the server, manually re-entering the data and it seemed to work.
Related
I'm trying to make a simple login page.I have to do it for university project.The problem is pretty simple, i'm trying to use redis to be the database for the users and passwords. The problem is that i can't extract the values out of the response that i get from redis.I got a docker running the redis image and every thing connect.In the example below im trying to make a simple boolean change from true to false according to the data inside the key (im using "a" as the key) but no matter what i do the value doesn't seem to change, it is note worthy that im very new to this and to js in particular, i read in the redis api that all of the funtions are asyncs i tried changing the code but it didnt help.
app.get('/enter', (req, res) => {
var username =req.query.user;
var password = req.query.pass;
ans = false
redis.get(username,function(err, reply) {
if(reply != null ) ans = true;
})
console.log(ans);
})
I just trying to verify that the key has a value, i tried to make a variable before and after the request but it isn't adjusting thanks for your time
I see you dont understand the very very basics of callbacks and asynchronouse behaviour of javascript.
Well you can code like this:
app.get('/enter', async (req, res) => {
var username =req.query.user;
var password = req.query.pass;
ans = false
let reply = await getUsername(username)
console.log(reply)
console.log(ans);
})
function getUsername(username) {
return new Promise((res, rej) => {
redis.get(username, function(err, reply) {
if(err) rej(err)
res(reply)
})
})
}
You can just promisfy your redis code with new Promise and then you can use async / await style on it
Otherwise you need to write your code in the callback witch leads to an callback hell if you have more code
Im testing my API with postman, when I try to send data in the URL Postman responds with 404 Not found. I guess Its the format but searching around I think its correct. Can anyone throw some light please?
But when I dont send any data in the URL it works just fine:
When I try to send data in the get request:
app.get("/mediciones/sigfox_libelium/:{device}", (req, res) => {
const { device } = req.params;
res.json("im in");
console.log("Im in");
console.log(device);
console.log(req.params.device);
When I send no data on the request works just fine(it crashes but its becouse its not finished yet):
app.get("/mediciones/sigfox_libelium", (req, res) => {
const { device} = req.params;
res.json("im in");
console.log("Im in");
console.log(device);
console.log(req.params.device);
My guess is you're using Express.js to build API right?
I think you use req.params in the wrong way.
If you want params name device
You have to use :device instead of :{device} in url path.
Like this
app.get("/mediciones/sigfox_libelium/:device", (req, res) => {
cosnt { device } = req.params // You can get device here
})
I'm new to javascript, node.js (or backend at all). I am trying to create a controller for the login page requests and I am confused about getting data from the MYSQL table and User Authentication and working with JWT package !
In my Controller, I first check if the user input is available in the user table (with a simple stored procedure), then I compare the database password and the user input, after this I want to create a token and with limited time. (I have watched some tutorial videos about JWT and there is no problem with it), my main problem is to figure out how to write a proper controller with this functions?
I have 2 other questions:
1.Is it the right and secure way to get data from MySQL table inside the route? Or should I create a JS class for my controller? (I'm a bit confused and doubtful here)
2.Assuming that comparePassword() returns true, how can I continue coding outside of the db.query callback function scope? Because I have to execute comparePasssword() inside db.query callback
loginController.js :
const { validationResult } = require('express-validator');
const bcrypt = require('bcrypt');
const db = require('../../sqlConnection')
let comparePassword = (dbPass, inputPass) => {
bcrypt.compare(inputPass, dbPass, function(err, result) {
console.log(result)
});
}
// for get request
exports.getController = (req, res) => {
res.send('login')
}
// for post request
exports.postController = (req, res) => {
let errors = validationResult(req)
if(!errors.isEmpty()) {
res.status(422).json({ errors: errors.array() })
}
// find data from MYSQL table
let sql = `CALL findUser(?)`
db.query(sql, [req.body.username], (err, res) => {
if(err) console.log(err)
//console.log(Object.values(JSON.parse(JSON.stringify(res[0]))))
var data = JSON.stringify(res[0])
data = JSON.parse(data).find(x => x)
data ? comparePassword(data.password, req.body.password) : res.status(400).send('cannot find
user')
})
res.send('post login')
}
login.js :
const express = require('express')
const router = express.Router()
const { check } = require('express-validator');
const loginCont = require('../api/controllers/loginController')
router.route('/')
.get(
loginCont.getController
)
.post(
[
check('username').isLength({min: 3}).notEmpty(),
check('password').isLength({min: 4}).notEmpty()
],
loginCont.postController
)
module.exports = router
In my point of view, looks like there is no easy answer for your question so I will try to give you some directions so you can figure out which are the gaps in your code.
First question: MySQL and business logic on controller
In a design pattern like MVC or ADR (please take a look in the links for the flow details) The Controllers(MVC) Or Actions(ADR) are the entry point for the call, and a good practice is to use these entry points to basically:
Instantiate a service/class/domain-class that supports the request;
Call the necessary method/function to resolve what you want;
Send out the response;
This sample project can help you on how to structure your project following a design pattern: https://riptutorial.com/node-js/example/30554/a-simple-nodejs-application-with-mvc-and-api
Second question: db and continue the process
For authentication, I strongly suggest you to take a look on the OAuth or OAuth2 authentication flow. The OAuth(2) has a process where you generate a token and with that token you can always check in your Controllers, making the service a lot easier.
Also consider that you may need to create some external resources/services to solve if the token is right and valid, but it would facilitate your job.
This sample project should give you an example about how to scope your functions in files: https://github.com/cbroberg/node-mvc-api
Summary
You may have to think in splitting your functions into scoped domains so you can work with them in separate instead of having all the logic inside the controllers, then you will get closer to classes/services like: authenticantion, user, product, etc, that could be used and reused amount your controllers.
I hope that this answer could guide you closer to your achievements.
I have a Node.js server which queries MySQL database. It serves as an api end point where it returns JSON and also backend server for my Express application where it returns the retrieved list as an object to the view.
I am looking into implementing flat-cache for increasing the response time. Below is the code snippet.
const flatCache = require('flat-cache');
var cache = flatCache.load('productsCache');
//get all products for the given customer id
router.get('/all/:customer_id', flatCacheMiddleware, function(req, res){
var customerId = req.params.customer_id;
//implemented custom handler for querying
queryHandler.queryRecordsWithParam('select * from products where idCustomers = ? order by CreatedDateTime DESC', customerId, function(err, rows){
if(err) {
res.status(500).send(err.message);
return;
}
res.status(200).send(rows);
});
});
//caching middleware
function flatCacheMiddleware(req, res, next) {
var key = '__express__' + req.originalUrl || req.url;
var cacheContent = cache.getKey(key);
if(cacheContent){
res.send(cacheContent);
} else{
res.sendResponse = res.send;
res.send = (body) => {
cache.setKey(key,body);
cache.save();
res.sendResponse(body)
}
next();
}
}
I ran the node.js server locally and the caching has indeed greatly reduced the response time.
However there are two issues I am facing that I need your help with.
Before putting that flatCacheMiddleware middleware, I received the response in JSON, now when I test, it sends me an HTML. I am not too well versed with JS strict mode (planning to learn it soon), but I am sure the answer lies in the flatCacheMiddleware function.
So what do I modify in the flatCacheMiddleware function so it would send me JSON?
I manually added a new row to the products table for that customer and when I called the end point, it still showed me the old rows. So at what point do I clear the cache?
In a web app it would ideally be when the user logs out, but if I am using this as an api endpoint (or even on webapp there is no guarantee that the user will log out the traditional way), how do I determine if new records have been added and the cache needs to be cleared.
Appreciate the help. If there are any other node.js caching related suggestions you all can give, it would be truly helpful.
I found a solution to the issue by parsing the content to JSON format.
Change line:
res.send(cacheContent);
To:
res.send(JSON.parse(cacheContent));
I created cache 'brute force' invalidation method. Calling clear method will clear both cache file and data stored in memory. You have to call it after db change. You can also try delete specified key using cache.removeKey('key');.
function clear(req, res, next) {
try {
cache.destroy()
} catch (err) {
logger.error(`cache invalidation error ${JSON.stringify(err)}`);
res.status(500).json({
'message' : 'cache invalidation error',
'error' : JSON.stringify(err)
});
} finally {
res.status(200).json({'message' : 'cache invalidated'})
}
}
Notice, that calling the cache.save() function will remove other cached API function. Change it into cache.save(true) will 'prevent the removal of non visited keys' (like mentioned in comment in the flat-cache documentation.
I have read all the questions on SO that I could find. They all use Express, Mongoose or they leave something out. I understand that Node.js is the server. I understand the MongoDB require is the driver the Node.js server uses to open a connection to the MongoDB. Then, on the server, I can do (from the documentation):
var MongoClient = require('mongodb').MongoClient;
var assert = require('assert');
var ObjectId = require('mongodb').ObjectID;
var url = 'mongodb://localhost:27017/test';
var findRestaurants = function(db, callback) {
var cursor =db.collection('restaurants').find( );
cursor.each(function(err, doc) {
assert.equal(err, null);
if (doc != null) {
console.dir(doc);
} else {
callback();
}
});
};
// Connect to the db
MongoClient.connect(url, function(err, db) {
assert.equal(null, err);
findRestaurants(db, function() { //I don't want to do this as soon as the server starts
db.close();
});
});
//if I put findRestaurant here,
function findRestaurant(data){
}
How do I call it from the client?
I do not want to find data as soon as I start the server. I realize those are examples, but what I cannot find is a way where the client requests some data and where the Node.js server returns it.
I have seen close examples using jQuery, Angular on the client, and then Express, Mongoose, Meteor, , etc.
All I want to understand is how I make this request from the client's browser. I can do that with XMLhttpRequest(), so I can put that part together, I believe. But, any example is appreciated.
But what is waiting on the Node.js side of things (how do I set up my function to be called once the server is listening)?
How do I create a function on the server side, maybe "GetRestaurants" and have that return the data it gets using find()?
I cannot find this information, this simple, anywhere. Is it too complicated to do the example without a framework?
I do not wish to copy and paste from something using Express, etc. without understanding what's going on. Most explanations never say, this goes on the Node.js side. This is client. I know I am expected to do my own research, but I am not putting it together, too used to RDBMSes, IIS, Apache, PHP, and so on.
I believe I have a fundamental misunderstanding of what's going on in the paradigm.
Please. No REST API creation, no frameworks of any kind on Node.js other than using the MongoDB library (unless there is an absolute requirement), not even jQuery, Angular, Jade, or anything else for the client side, straight up JavaScript on all sides.
I have seen questions like this,
How to display data from MongoDB to the frontend via Node.js without using a framework
But they do not show what I am asking. They do it all at once, as soon as the database connects. What if I want to do a delete or insert or find? There are many SO questions like this, but I have not hit the one that shows what I am looking for.
This should give the guidance. Once you go to a browser and type http://localhost:5155 the callback function (request, response) { will be called and the request to db will be made. Make sure you get response and then start working on the client side code:
const http = require('http');
const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
const url = 'mongodb://localhost:27017/test';
const server = http.createServer(function (request, response) {
getData(function (data) {
response.end(data);
});
});
function getData(callback) {
// Connect to the db
MongoClient.connect(url, function (err, db) {
assert.equal(null, err);
findRestaurants(db, function (data) {
db.close();
callback(data);
});
});
const findRestaurants = function (db, callback) {
const cursor = db.collection('restaurants').find();
const data = [];
cursor.each(function (err, doc) {
assert.equal(err, null);
data.push(doc);
if (doc === null) {
callback(data);
}
});
};
}
server.listen(5155);