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Live username availability check in node express.js and client side js

I am making an express, MongoDB, and handlebars(templating engine) web app with a form that lets users create their unique username. Now I want to display a little tooltip after set intervals to display whether the username is available or not. The way I have done it is by exposing an endpoint with JSON data about usernames
api.get("/usernames", (req, res)=>{
users.find({}, (err, users)=>{
let out = []
users.forEach(user=>{
out.push(user.uname)
})
})
res.json({usernames: out})
})
And then I fetch the data and loop through the array on the client-side. But I don't think this method would scale very well. Is there an easier and more scalable way to achieve this??

try this
api.get("/usernames", (req, res)=>{
users.find({}, (err, users)=>{
let out = users.filter(x=>x.uname===req.body.name)
let result = out.length?"Already exists": "Available"
})
res.json({result: result})
})

Error with get request for users

When using a get request for all the users in my database (see code below) i only get the "first" user in the database. If i instead try to use the "findOne"-method i get the same user as before no matter what i put in (the username doesn't even have to be in the db it still gives me the same user). I've been trying to understand why this isn't working but can't find any problems with the code. Could it be a problem with db settings or something similar? All help is appreciated!
In AuthController:
// Get all users
AuthController.allusers = function(req, res) {
User.find({}, function(err, users) {
}).then(function(users) {
res.json({users: users});
});
}
In routes:
// GET Routes.
router.get('/users', AuthController.allusers);

Since you are using Sequelizejs, you might want to do findAll.
AuthController.allusers = function(req, res) {
User.findAll().then(function (users) {
res.send({users: users});
}
}
According to the docs:
find - Search for one specific element in the database
findAll - Search for multiple elements in the database

Creating a user session - NODE js

I am new to node js & javascript in general. I have the below piece of code that will handle a login. I have a MYSQL database with a customer table. When the customer enters their username and password, it checks does it exist in the database. This part is working.
I now want to enhance this feature so that it will take the username and create some sort of a session variable, which can be used across the application. I am new to JS so I am not yet sure which inbuilt facilities already exist, or best practice around sessions.
I want to be able to use this session variable across the application, and for subsequent logout facility.
Can someone advise me on this, or point me in the right direction? Thanks.
case "/login":
var body = '';
console.log("user Login ");
request.on('data', function (data) {
body += data;
});
request.on('end', function () {
var obj = JSON.parse(body);
console.log(JSON.stringify(obj, null, 2));
var query = "SELECT * FROM Customer where name='"+obj.name+"'";
response.writeHead(200, {
'Access-Control-Allow-Origin': '*'
});
db.query(
query,
[],
function(err, rows) {
if (err) {
response.end('{"error": "1"}');
throw err;
}
if (rows!=null && rows.length>0) {
console.log(" user in database" );
theuserid = rows[0].customerID;
var obj = {
id: theuserid
}
response.end(JSON.stringify(obj));
}
else{
response.end('{"error": "1"}');
console.log(" user not in database");
}
}
);
});
}

There can be multiple ways of implementing a user session.
One, you could use a browser cookie, it comes with many pros and cons and you should read about it a bit to see how its managed. This would also depend on the server you are using (express, hapi, etc).
Two, you can set a JWT token on the backend, and include it in the header of the response, then you can either use your application state or the local storage of the browser to save that token on the UI. Any such follow up requests requiring authentication should contain this auth token as a header for verification.
For more clarity, you can look into related libraries (such as passport), which make this task a lot easier.
PS: If you choose cookies, please make sure the business is going to allow it or not as the end-users do not like being tracked always. :)

How can I dynamically assign a database path in Express.js based on login?

I have a backend service that I would like to use as a single point of entry for my web application, and dynamically assign a database path based on the user login.
I realize that this is not a scalable solution. I intend to use it during a testing period with several clients (accessing the ALPHA database), and also setting up a demo (accessing the SAND database).
I have the following module that I have written as a simple test to see if the login is for the demo user, all other logins will go to the other resource:
config.js
var express = require('express');
var app = express();
module.exports.dbPath = function (login){
console.log('login - ', login);
if (login === 'demo#mysite.com'){
return process.env.DB_SAND;
} else {
return process.env.DB_ALPHA;
}
};
My question is, how can I manage each unique login and assign a globally accessible reference for that session to direct each user session consistently to the correct database?
Am I overcomplicating this? If there is a different approach that would be a better practice I would welcome a suggestion in another direction.

I would use it as a middleware, and attach it to the req object for each user, something similar this:
module.exports = {
dbPath: function(req, res, next){
var login = req.body.login;
console.log('login - ', login);
if (login === 'demo#mysite.com'){
req.dbPath = 'DB_SAND';
} else {
req.dbPath = 'DB_ALPHA';
}
next();
}
};

What does a Node.js web service look like?

I am taking a look at Node.js and thinking about using it for building an API. From what I can tell, ExpressJS would be the web framework and is not what I'd be looking for to solve this.
So what would a web service look like? Would it simply be creating a server, talking to mongo and returning results? Also, what does routing look like? (I'd obviously want to 'design' the routes).

If Express would be your web framework, look at the express-resource (Github) middleware for routing an API. You define resources and it'll wire up REST-style routing for you with very little boilerplate.
app.resource('horses', require('./routes/horses'), { format: json })
Given the above, express-resource will hook up all the REST-style routes to actions you supply, returning JSON by default. In routes/horses.js, you export actions for that resource, along the lines of:
exports.index = function index (req, res) {
// GET http://yourdomain.com/horses
res.send( MyHorseModel.getAll() )
}
exports.show = function show (req, res) {
// GET http://yourdomain.com/horses/seabiscuit
res.send( MyHorseModel.get(req.params.horse) )
}
exports.create = function create (req, res) {
// PUT http://yourdomain.com/horses
if (app.user.canWrite) {
MyHorseModel.put(req.body, function (ok) { res.send(ok) })
}
}
// ... etc
You can respond with different representations:
exports.show = {
json: function (req, res) {
// GET http://yourdomain/horses/seabiscuit.json
}
, xml: function (req, res) {
// GET http://yourdomain/horses/seabiscuit.xml
}
}
Middlewares like express-resource can make life with Node and Express much easier, take a look through the examples on github to see if it'll do what you need.

Here is a stub that looks up a horse name from a Postgres database and returns the result as JSON. Clients would access would access the API by going to address such as http://yourdomain.com/api/horse/seabiscuit
app.get('/api/horse/:name', function(req, res){
pg.connect(conString, function(err, client) {
var horse = req.params.name;
var sql = "...";
client.query(sql, function(err, result) {
if (err) {
...
}
for (var i=0; i<result.rows.length; i++) {
// Customize data as needed
}
return res.send(JSON.stringify(result.rows));
});
});
});

Node is pretty low level. It's like C in JavaScript's clothing. Since it's comparable to C, there's pretty much a lot you can do with Node. Creating web servers is just one of them. You can create live chat servers using sockets, blogs, streaming etc. The possibilities are infinite. You are limited only by your imagination.
Routing is just a task where you take in commands (commonly via URL or headers) and do tasks based on those commands passed.
But even I have not yet scathed the surface of node. It's API is huge and getting bigger. Better try using some basic library like Express or Connect first since they pretty much abstract the basic requirement of building the server from code.