What is Node js Connect Express and middleware

Question

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

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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  quot middleware quot

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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

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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

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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

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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  lt appname gt   then open http   localhost 3000 and see  Now you are in

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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

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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

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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] What is Node.js' Connect, Express and "middleware"?

The stupid simple answer

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