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Communication between an express node server and its displaying html

Really fast, this question may have already been asked, but I am not totally clear on the terminology and have had no success when searching for a solution.
I am attempting to create a simple web application that can receive get and post requests. Then, I would like to take the information I receive from these requests and use them in a javascript file embedded in html that is displayed. I think it may be more clear with code. This is my app.js:
var express = require('express');
var app = express();
var assert = require('assert');
app.use(express.static('javascript'));
app.get('/', function(req, res) {
res.render('index.jade');
});
app.listen(3000);
I would then like to be able to take information received from a get or post request, specifically in JSON format, and then be able to use it in javascript that I have linked to index.jade. To make matters slightly more confusing in index.jade the only line is:
include map.html
So ideally I would be able to get the information to javascript in that html file.
I want to be able to pretty continuously update map.html using javascript based on frequent get and post commands.
This could be a very simple solution, I am pretty new with web application programming in general, and I have been struggling with this problem. Thanks in advance, and ask if you need any clarification.

I think you need to understand what you are doing. You are creating a web server using node.js. Express framework simplifies that for you. The official documentation of express is pretty great. You should refer that especially this link.
Now, in your application, you need to create endpoints for GET and POST requests. You have already created one endpoint "/" (root location) that loads your home page which is the contents of the file index.jade. A small example is :
app.get('/json', function (req, res) {
res.setHeader('Content-Type', 'application/json');
res.send(JSON.stringify({ a: 1 }));
});
Jade is a templating engine which resolves to HTML. You should refer its documentation as well. Since as you said, you are not very familiar with these, you could simply use HTML as well.
After this tasks are quite simple. In your javascript, using ajax calls you can access the GET or POST endpoints of your server and do the desired actions.
Hope it helps!

The way I get it you want to be able to call an endpoint (lets assume /awesome) pass some info and then write to a Javascript file that you can then reference in your html.
Something like the below would write a main.js file in your public folder. You can make it write whatever you want.
var fs = require('fs');
fs.writeFile("/public/main.js", "console.log('Hello!')", function(err) {
if(err) {
return console.log(err);
}
console.log("The file was saved!");
});
You can then reference /public/main.js in your html.
Check that: Writing files in Node.js
If I misunderstood your intentions, apologies. :)

So you want to reviece continuously data from the server maybe web sockts are an option for you http://socket.io/docs/
This way u will open a stable connection from the client to the server. This is a great way if u want to get updates done by other clients.
If you want to trigger the changes by the client then ajaxs calls(http://www.w3schools.com/ajax/) as hkasera mentioned are the way to go.

How to use node.js as gate to a website

I got an old website on a webserver. It is to big and not structured well enough but needs to be improved by e.g. Account management. As it is (in my opinion) at its end of lifetime, we do not want to put more effort in it but instead migrate to new technology. For that, we want to use node.js and AngularJS, because the whole project is more a webapp than it was at the beginning. As a migration concept, we want to include the old stuff via a kind of routing through the node.js server and replace it step by step. For that I looked into the "request" library without getting the right grip.
Goal is, to route some requests after authorization check to the old server, without leaving the new server (gate). For that I need to check and parse the gets and posts. Some other requests have to response by the node.js server itself.
As I think that I am not the only one with that approach I am asking for experience in that matter.

I had to do something similar, because we made a new API which was not compatible with the first version and some features were not implemented in the newer API so we had to do like a bridge. Authentication was happening in the first server, and then we were routing the request to the old API and then returning to the user.
The approach I took was using a module like request to make the call in the old server.
Assuming you are using expres for your new API, you can do something similar
var request = require('request');
app.get('/test', function(req, res) {
//authenticate stuff
var options = {
url: 'http://oldendpoint.com/test',
headers: {
//headers for authenticate in the old endpoint
}
};
request(options, function (error, response, body) {
if (!error && response.statusCode == 200) {
res.send(body); //this will send it back to your client
}
});
});
Basically you get a request to your new API (node.js app) in the /test endpoint and this, after auth or after whatever check, will forward the request to the old system, and then it will return some data which is forwarded to the client who made the request in the first place.

Understanding how to use NodeJS to create a simple backend

I have been trying to develop a rather simple server in nodejs. Basically, what I am going for is a simple API that requires authentication (simple username/password style). What I do not need is any kind of frontend functionality (templating etc.). My problem is, I can't seem to get my head around the approach of express/node.
Specifically, my questions are:
How do I wire in the authentication? Do I pass several handlers into every route that requires authentication, or is there a more elegant way to do this?
How does the Express middleware (like app.use(express.bodyParser())) work? Do they alter contents of the request or response object? Specifically, if I use the body parser (internally formidable?), where do I access the request data this is supposed to parse?
When using authentication and I have, say, credentials stored in a database with more information about the individual client associated, at what point do I extract that information? I.e., when a user logs in, do I fetch the user record on login and pass it on, or do I fetch it in every handler that requires the information?
Ultimately, do you know of an open source application that I could take a look at? I'd like to see something that has simple authentication and maybe even utilizes formidable, since uploading a file is one of my requirements.
As I mentioned earlier, I believe my problem is ultimately a difficulty with the function-oriented approach in node (also, I have rather limited experience in webservice programming). If you know a resource where I could read up on how to approach architecting a nodejs app, please don't hesitate to point me to it.

How do I wire in the authentication? Do I pass several handlers into
every route that requires authentication, or is there a more elegant
way to do this?
You should use the session middleware. Here is some pseudo code:
var http = require('http');
var app = express();
var authorize = function(req, res, next) {
if(req.session && req.session.appname && req.session.appname === true) {
// redirect to login page
return;
}
next();
}
app.use(express.session());
app.all('/admin*', authorize, function(req, res, next) {
});
How does the Express middleware (like app.use(express.bodyParser()))
work? Do they alter contents of the request or response object?
Specifically, if I use the body parser (internally formidable?), where
do I access the request data this is supposed to parse?
Every middleware have an access to the request and response object. So, yes, it modifies it. Normally attach properties to it. This means that inside your handler (which is also a middleware) you may write:
if(req.body && req.body.formsubmitted && req.body.formsubmitted === 'yes') {
var data = {
title: req.body.title,
text: req.body.text,
type: req.body.type
}
// store the data
}
When using authentication and I have, say, credentials stored in a
database with more information about the individual client associated,
at what point do I extract that information? I.e., when a user logs
in, do I fetch the user record on login and pass it on, or do I fetch
it in every handler that requires the information?
I think that you should do the things the same way as in any other server side language. Keep the state of the user (logged/not-logged) inside a session. You may also keep the user's id and fetch the data for him whatever you need. It depends of your case, but you have the ability to cache information. Because node is not like PHP for example, I mean it's not dieing.
Ultimately, do you know of an open source application that I could
take a look at? I'd like to see something that has simple
authentication and maybe even utilizes formidable, since uploading a
file is one of my requirements.
Yep. I wrote an article about really simple MVC web site with admin panel. It is available here. And the code of it is here.

A simple way to implement authentication (if you don't want to use additional modules):
var checkAuth = function(req, res, next) {
if(!req.session.user)
{
// Redirect to login form
res.redirect("/login");
}
else
{
// Proceed to member's area
next();
}
};
app.get("/member/page", checkAuth, function(req, res) {
// render view, etc
});
bodyParser parses / converts the body of a POST request into an object, which helps with getting form submission values.
The route that handles your login form submission can access username / password like this:
var username = req.body.username;
var password = req.body.password;
At this point you'd query your database to select from users where the username and password matches (you'd want to use password encryption in a production environment).
If you get a record back in the query result, set it in the session. A simple way to do this is:
req.session.user = userRecord
(Adjust for your session middleware)

If you are looking for REST, I recommend using either Restify or booster
For authentication (distinct from authorization), use standard Basic, which can be handled by express.basicAuth() just to parse it and place it on the req object. Personally, I don't like basicAuth because it returns a 401 if there is no login, whereas the process of authenticating is different than determining if authentication is necessary.
For more advanced authentication, as well as session management, use cansecurity or passport. For authorization, you either can put individual middleware in each route, use cansecurity's middlewares, or use its declarative authorization.
Disclosure: I am the author of both booster and cansecurity.

If your goal is to build a RESTful API in Node.js, my best bet would be Restify, which uses a similar aproach of routes like Express, but eliminates all the high level stuff(templating, etc.) and ads backend functionalities(ie: body parser, ip blacklist, requests per hour).
For the authentication part, I would use another library perhaps, and wire it to a particular route. There are ORM's too that can solve your database needs(mongo and mysql are well supported, both for the "noSQL" fans and the classic db aproach ones).

How to integrate derby.js with express.js in node.js?

I am using express framework for my Node App. I need to have some real time updates like notifications in facebook. What I need is integrate derby.js(which is framework build on the top of express) only for real time notification triggering in express App. How can I accomplish this task?
Expressjs syntax I am using
app.get('/', function(req, res){
//other things as fetch query
res.render('index', { notificationcount : 0 });
});
Above thing will take notification count from database and displayed in view.
Derbyjs sample syntax for real time update
app.view.make('Body'
, 'Notications: <div>{notificationcount}</div>'
);
app.get('/', function (page, model) {
// Subscribe specifies the data to sync
model.subscribe('notificationcount', function () {
page.render();
});
});
What I need is only one section(box with notification count) from express rendered view page needs come from derby. So that the box will updated on real time updates on Database.
How we can integrate derby view in express? Is it possible?

Derby is a full-featured alpha framework for building real-time apps. It seems like you only need a small amount of real-time for specific functionality. I'd recommend just using socket.io or sockjs - no need to integrate an entire framework for one tiny use case.

Well, not sure where you bought the syntax, but
change {notificationcount} to {{notificationcount}} ...
and render the page correctly
page.render('index', { notificationcount : 0 });
whenever your model changes, site will change live.
You should install and study the examples ::
https://github.com/codeparty/derby-examples

Relationship of node.js / Express / Connect / Socket.io

I'm confused. The main question I have is, when to use pure node.js, when shall I use a framework/MVC like "express" or "connect".
I know that "express" is just adding a bunch of functionality to "connect", but what is it really good for? Lets say, I want all my HTTP stuff do against an "Apache" server and only do some partial stuff with node.js (like WebSocket connections, CouchDB, etc.).
Would it make sense in this scenario to use "express" or "connect" for some reason?
As far as I know, Socket.IO also handles HTTP requests as a fallback, so would it be just enough to use Socket.IO for those needs ?
What else is the big advantage using Express/Connect ?

Express (or Connect) is an application framework for HTTP web applications. It's the entry point of your application. It provides some very common functionnalities such as :
HTTP Server
URL Routing
Request args
Sessions
It also allows other functionnalities to be easily used (they are called middleware) such as Authentication handling, templating.
If you just want to implement a pub/sub service through SocketIO, without any pages or other API, just use the Socket.io library (S.io homepage example) :
var io = require('socket.io').listen(80);
io.sockets.on('connection', function (socket) {
socket.emit('news', { hello: 'world' });
socket.on('my other event', function (data) {
console.log(data);
});
});
If you want to use Socket.io within a more complexe application, serving pages and API, you can (must ?) integrate it with Express (see How To Use)

Hi I have been using Expressjs for some time now and find it particularly useful for the Jade templating engine it provides by default. Jade is a new templating language and though I admit it takes some time to get familiar with it, its pretty useful. You can write conditionals, mixins, pass variables to your pages, use partials etc. It just makes client side html really easy. Also expressjs sets up your view, javascript, stylesheets directory structure... If followed properly catching responses and rendering html pages are a matter of couple of line of codes. As discussed above, the http middlewear is a lot easier to implement..