Despite knowing JavaScript quite well, I'm confused what exactly these three projects in Node.js ecosystem do. Is it something like Rails' Rack? Can someone please explain?
[Update: As of its 4.0 release, Express no longer uses Connect. However, Express is still compatible with middleware written for Connect. My original answer is below.]
I'm glad you asked about this, because it's definitely a common point of confusion for folks looking at Node.js. Here's my best shot at explaining it:
Node.js itself offers an http module, whose createServer method returns an object that you can use to respond to HTTP requests. That object inherits the http.Server prototype.
Connect also offers a createServer method, which returns an object that inherits an extended version of http.Server. Connect's extensions are mainly there to make it easy to plug in middleware. That's why Connect describes itself as a "middleware framework," and is often analogized to Ruby's Rack.
Express does to Connect what Connect does to the http module: It offers a createServer method that extends Connect's Server prototype. So all of the functionality of Connect is there, plus view rendering and a handy DSL for describing routes. Ruby's Sinatra is a good analogy.
Then there are other frameworks that go even further and extend Express! Zappa, for instance, which integrates support for CoffeeScript, server-side jQuery, and testing.
Here's a concrete example of what's meant by "middleware": Out of the box, none of the above serves static files for you. But just throw in connect.static (a middleware that comes with Connect), configured to point to a directory, and your server will provide access to the files in that directory. Note that Express provides Connect's middlewares also; express.static is the same as connect.static. (Both were known as staticProvider until recently.)
My impression is that most "real" Node.js apps are being developed with Express these days; the features it adds are extremely useful, and all of the lower-level functionality is still there if you want it.
The accepted answer is really old (and now wrong). Here's the information (with source) based on the current version of Connect (3.0) / Express (4.0).
What Node.js comes with
http / https createServer which simply takes a callback(req,res) e.g.
var server = http.createServer(function (request, response) {
// respond
response.write('hello client!');
response.end();
});
server.listen(3000);
What connect adds
Middleware is basically any software that sits between your application code and some low level API. Connect extends the built-in HTTP server functionality and adds a plugin framework. The plugins act as middleware and hence connect is a middleware framework
The way it does that is pretty simple (and in fact the code is really short!). As soon as you call var connect = require('connect'); var app = connect(); you get a function app that can:
Can handle a request and return a response. This is because you basically get this function
Has a member function .use (source) to manage plugins (that comes from here because of this simple line of code).
Because of 1.) you can do the following :
var app = connect();
// Register with http
http.createServer(app)
.listen(3000);
Combine with 2.) and you get:
var connect = require('connect');
// Create a connect dispatcher
var app = connect()
// register a middleware
.use(function (req, res, next) { next(); });
// Register with http
http.createServer(app)
.listen(3000);
Connect provides a utility function to register itself with http so that you don't need to make the call to http.createServer(app). Its called listen and the code simply creates a new http server, register's connect as the callback and forwards the arguments to http.listen. From source
app.listen = function(){
var server = http.createServer(this);
return server.listen.apply(server, arguments);
};
So, you can do:
var connect = require('connect');
// Create a connect dispatcher and register with http
var app = connect()
.listen(3000);
console.log('server running on port 3000');
It's still your good old http.createServer with a plugin framework on top.
What ExpressJS adds
ExpressJS and connect are parallel projects. Connect is just a middleware framework, with a nice use function. Express does not depend on Connect (see package.json). However it does the everything that connect does i.e:
Can be registered with createServer like connect since it too is just a function that can take a req/res pair (source).
A use function to register middleware.
A utility listen function to register itself with http
In addition to what connect provides (which express duplicates), it has a bunch of more features. e.g.
Has view engine support.
Has top level verbs (get/post etc.) for its router.
Has application settings support.
The middleware is shared
The use function of ExpressJS and connect is compatible and therefore the middleware is shared. Both are middleware frameworks, express just has more than a simple middleware framework.
Which one should you use?
My opinion: you are informed enough ^based on above^ to make your own choice.
Use http.createServer if you are creating something like connect / expressjs from scratch.
Use connect if you are authoring middleware, testing protocols etc. since it is a nice abstraction on top of http.createServer
Use ExpressJS if you are authoring websites.
Most people should just use ExpressJS.
What's wrong about the accepted answer
These might have been true as some point in time, but wrong now:
that inherits an extended version of http.Server
Wrong. It doesn't extend it and as you have seen ... uses it
Express does to Connect what Connect does to the http module
Express 4.0 doesn't even depend on connect. see the current package.json dependencies section
node.js
Node.js is a javascript motor for the server side.
In addition to all the js capabilities, it includes networking capabilities (like HTTP), and access to the file system.
This is different from client-side js where the networking tasks are monopolized by the browser, and access to the file system is forbidden for security reasons.
node.js as a web server: express
Something that runs in the server, understands HTTP and can access files sounds like a web server. But it isn't one.
To make node.js behave like a web server one has to program it: handle the incoming HTTP requests and provide the appropriate responses.
This is what Express does: it's the implementation of a web server in js.
Thus, implementing a web site is like configuring Express routes, and programming the site's specific features.
Middleware and Connect
Serving pages involves a number of tasks. Many of those tasks are well known and very common, so node's Connect module (one of the many modules available to run under node) implements those tasks.
See the current impressing offering:
logger request logger with custom format support
csrf Cross-site request forgery protection
compress Gzip compression middleware
basicAuth basic http authentication
bodyParser extensible request body parser
json application/json parser
urlencoded application/x-www-form-urlencoded parser
multipart multipart/form-data parser
timeout request timeouts
cookieParser cookie parser
session session management support with bundled MemoryStore
cookieSession cookie-based session support
methodOverride faux HTTP method support
responseTime calculates response-time and exposes via X-Response-Time
staticCache memory cache layer for the static() middleware
static streaming static file server supporting Range and more
directory directory listing middleware
vhost virtual host sub-domain mapping middleware
favicon efficient favicon server (with default icon)
limit limit the bytesize of request bodies
query automatic querystring parser, populating req.query
errorHandler flexible error handler
Connect is the framework and through it you can pick the (sub)modules you need.
The Contrib Middleware page enumerates a long list of additional middlewares.
Express itself comes with the most common Connect middlewares.
What to do?
Install node.js.
Node comes with npm, the node package manager.
The command npm install -g express will download and install express globally (check the express guide).
Running express foo in a command line (not in node) will create a ready-to-run application named foo. Change to its (newly created) directory and run it with node with the command node <appname>, then open http://localhost:3000 and see.
Now you are in.
Connect offers a "higher level" APIs for common HTTP server functionality like session management, authentication, logging and more. Express is built on top of Connect with advanced (Sinatra like) functionality.
Node.js itself offers an HTTP module, whose createServer method returns an object that you can use to respond to HTTP requests. That object inherits the http.Server prototype.
Related information, especially if you are using NTVS for working with the Visual Studio IDE. The NTVS adds both NodeJS and Express tools, scaffolding, project templates to Visual Studio 2012, 2013.
Also, the verbiage that calls ExpressJS or Connect as a "WebServer" is incorrect. You can create a basic WebServer with or without them. A basic NodeJS program can also use the http module to handle http requests, Thus becoming a rudimentary web server.
middleware as the name suggests actually middleware is sit between middle.. middle of what? middle of request and response..how request,response,express server sit in express app
in this picture you can see requests are coming from client then the express server server serves those requests.. then lets dig deeper.. actually we can divide this whole express server's whole task in to small seperate tasks like in this way.
how middleware sit between request and response small chunk of server parts doing some particular task and passed request to next one.. finally doing all the tasks response has been made..
all middle ware can access request object,response object and next function of request response cycle..
this is good example for explaining middleware in express youtube video for middleware
The stupid simple answer
Connect and Express are web servers for nodejs. Unlike Apache and IIS, they can both use the same modules, referred to as "middleware".
I'm really confused. I started learning to use node.js with MEAN stack. Before I used webpack and browserfy without really understanding it.
What confuses me is the following:
Express fires up a server and I can handle the requests
Webpack fires up a server
Browserify fires up a server
simply typing in plain js e.g. var http = require('http'); http.createServer(function (req, res) { ... fires up a server
Well, Webpack and Browserfy (as far as I understand) also bundle js files. How does the logic "under the hood" works and do they bundle everything I code and send it to the client (E.g. my DB login)?
I read this one Webpack vs webpack-dev-server vs webpack-dev-middleware vs webpack-hot-middleware vs etc , which told me webpack uses express under the hood. So maybe express also uses the plan .js server under the hood?
Well, I can go on like this forever. I am a little confused.
Well, what and where are the differences and how do thee apps work (together)?
First of all express use the core API and module of node.js like http module .
express uses the http module to create the server at specific port so
app.listen(3000);
will simple be like this
var http = require('http);
var server = http.createServer() ;
server.listen(3000) ;
server.on('request',function(req,res){
// here express will do all its magic
// and handle the request and response for you under the hood
})
Second things is that webpack and other bundling tools is used for bundling files and assets in the front end not the back end and they can create simple server for listening for changes in your files to give you other features like
+ live reload
+ hot module replacement
but also you can use webpack in the back end to use things like babel-loader or use the hot module replacement feature
so express works for the back end
and webpack use it in the front end
you can create different ports on each server and communicate between them via ajax API like fetch
and that's how actually it should work .
learn more
understanding express.js
understanding express and node fundamentals
webpack.js concepts and documentation
What's the difference between creating a server using http module and creating a server using express framework in node js?
Thanks.
Ultimately, express uses node's http api behind the scenes.
express framework
The express framework provides an abstraction layer above the vanilla http module to make handling web traffic and APIs a little easier. There's also tons of middleware available for express (and express-like) frameworks to complete common tasks such as: CORS, XSRF, POST parsing, cookies etc.
http api
The http api is very simple and is used to to setup and manage incoming/outgoing ,HTTP connections. Node does most of the heavy lifting here but it does provide things you'll commonly see throughout most node web framework such as: request/response objects etc.
Express uses the http module under the hood, app.listen() returns an instance of http. You would use https.createServer if you needed to serve your app using HTTPS, as app.listen only uses the http module.
Here's the source for app.listen so you can see the similarities.:
app.listen = function(){
var server = http.createServer(this);
return server.listen.apply(server, arguments);
};
Koa and Express 4.0 are both fairly new, and from what I've read, Koa was made by the Express team.
From what I understand, Koa requires features of node that are only available in 0.11 (the unstable branch) of node, and also uses generators. Express 4.0 seems to only be the next version of the Express framework.
Are there any differences I am missing completely? Is it likely (based on what the Express team has publicly stated) that Koa and Express will merge at some point in the future?
Thanks!
Search engines should be your first resort before posting open-ended questions.
From the Koa docs:
Koa vs Express
Philosophically, Koa aims to "fix and replace node", whereas Express "augments node". Koa uses co to rid apps of callback
hell and simplify error handling. It exposes its own this.request and
this.response objects instead of node's req and res objects.
Express, on the other hand, augments node's req and res objects with
additional properties and methods and includes many other "framework"
features, such as routing and templating, which Koa does not.
Thus, Koa can be viewed as an abstraction of node.js's http modules,
where as Express is an application framework for node.js.
...
Does Koa replace Express?
It's more like Connect, but a lot of the Express goodies were moved to
the middleware level in Koa to help form a stronger foundation. This
makes middleware more enjoyable and less error-prone to write, for the
entire stack, not just the end application code.
Typically many middleware would re-implement similar features, or even
worse incorrectly implement them, when features like signed cookie
secrets among others are typically application-specific, not
middleware specific.
...
Why isn't Koa just Express 4.0?
Koa is a pretty large departure from what people know about Express,
the design is fundamentally much different, so the migration from
Express 3.0 to this Express 4.0 would effectively mean rewriting the
entire application, so we thought it would be more appropriate to
create a new library.
Koa does not provides functionalities like Routing, Templating, Sending files and JSONP while the express does.
koa exposes its own ctx.request and ctx.response objects instead of node's req and res objects i.e. functions of the form (req, res, next), are incompatible with Koa.
Koa can be viewed as an abstraction of node.js's http modules, where as Express is an application framework for node.js.
For more detailed answer you can visit official documents on this link :
https://github.com/koajs/koa/blob/master/docs/koa-vs-express.md
I'm creating an Express.js API on a Node.js server. The API is used to access data stored on the server. I also keep a log of who's accessing the API in a database.
I'm trying to create an admin section that will use Angular.js to display the admin access logs neatly. I used the Angular Express Bootstrap seed to start my project:
https://github.com/jimakker/angular-express-bootstrap-seed/
My problem is that I need the controllers.js to access node modules but it doesn't seem to know that node exists. Here is my error:
controller.js
var mongo = require('mongodb');
[Uncaught ReferenceError: require is not defined]
How can I use node modules in Angular.js files?
Node is a server side technology, you would not typically use your node modules on the browser with Angular.js. However, if you want commonjs require functionality in the browser see: https://github.com/substack/node-browserify.
Ofcourse, a browser can't talk to mongodb directly which is why you need an API in the first place, angular would communicate with your API using HTTP.
Angular.js makes an $http call to Node.js which requires and talks to the mongodb.