Things have changed once again starting Express 4.16.0, you can now use express.json() and express.urlencoded() just like in Express 3.0.

This was different starting Express 4.0 to 4.15:

$ npm install --save body-parser

and then:

var bodyParser = require('body-parser')
app.use( bodyParser.json() );       // to support JSON-encoded bodies
app.use(bodyParser.urlencoded({     // to support URL-encoded bodies
  extended: true
})); 

The rest is like in Express 3.0:

Firstly you need to add some middleware to parse the post data of the body.

Add one or both of the following lines of code:

app.use(express.json());       // to support JSON-encoded bodies
app.use(express.urlencoded()); // to support URL-encoded bodies

Then, in your handler, use the req.body object:

// assuming POST: name=foo&color=red            <-- URL encoding
//
// or       POST: {"name":"foo","color":"red"}  <-- JSON encoding

app.post('/test-page', function(req, res) {
    var name = req.body.name,
        color = req.body.color;
    // ...
});

Note that the use of express.bodyParser() is not recommended.

app.use(express.bodyParser());

...is equivalent to:

app.use(express.json());
app.use(express.urlencoded());
app.use(express.multipart());

Security concerns exist with express.multipart(), and so it is better to explicitly add support for the specific encoding type(s) you require. If you do need multipart encoding (to support uploading files for example) then you should read this.

Note: this answer is for Express 2. See here for Express 3.

If you're using connect/express, you should use the bodyParser middleware: It's described in the Expressjs guide.

// example using express.js:
var express = require('express')
  , app = express.createServer();
app.use(express.bodyParser());
app.post('/', function(req, res){
  var email = req.param('email', null);  // second parameter is default
});

Here's the original connect-only version:

// example using just connect
var connect = require('connect');
var url = require('url');
var qs = require('qs');
var server = connect(
  connect.bodyParser(),
  connect.router(function(app) {
    app.post('/userlogin', function(req, res) {
      // the bodyParser puts the parsed request in req.body.
      var parsedUrl = qs.parse(url.parse(req.url).query);
      var email = parsedUrl.email || req.body.email;;
    });
  })
);

Both the querystring and body are parsed using Rails-style parameter handling (qs) rather than the low-level querystring library. In order to parse repeated parameters with qs, the parameter needs to have brackets: name[]=val1&name[]=val2. It also supports nested maps. In addition to parsing HTML form submissions, the bodyParser can parse JSON requests automatically.

Edit: I read up on express.js and modified my answer to be more natural to users of Express.

Given some form:

<form action='/somepath' method='post'>
   <input type='text' name='name'></input>
</form>

Using express

app.post('/somepath', function(req, res) {

    console.log(JSON.stringify(req.body));

    console.log('req.body.name', req.body['name']);
});

Output:

{"name":"x","description":"x"}
req.param.name x

app.use(express.bodyParser());

Then for app.post request you can get post values via req.body.{post request variable}.

Security concern using express.bodyParser()

While all the other answers currently recommend using the express.bodyParser() middleware, this is actually a wrapper around the express.json(), express.urlencoded(), and express.multipart() middlewares (http://expressjs.com/api.html#bodyParser). The parsing of form request bodies is done by the express.urlencoded() middleware and is all that you need to expose your form data on req.body object.

Due to a security concern with how express.multipart()/connect.multipart() creates temporary files for all uploaded files (and are not garbage collected), it is now recommended not to use the express.bodyParser() wrapper but instead use only the middlewares you need.

Note: connect.bodyParser() will soon be updated to only include urlencoded and json when Connect 3.0 is released (which Express extends).

So in short, instead of ...

app.use(express.bodyParser());

...you should use

app.use(express.urlencoded());
app.use(express.json());      // if needed

and if/when you need to handle multipart forms (file uploads), use a third party library or middleware such as multiparty, busboy, dicer, etc.

You shoudn't use app.use(express.bodyParser()). BodyParser is a union of json + urlencoded + mulitpart. You shoudn't use this because multipart will be removed in connect 3.0.

To resolve that, you can do this:

app.use(express.json());
app.use(express.urlencoded());

It´s very important know that app.use(app.router) should be used after the json and urlencoded, otherwise it does not work!

Note for Express 4 users:

If you try and put app.use(express.bodyParser()); into your app, you'll get the following error when you try to start your Express server:

Error: Most middleware (like bodyParser) is no longer bundled with Express and must be installed separately. Please see https://github.com/senchalabs/connect#middleware.

You'll have to install the package body-parser separately from npm, then use something like the following (example taken from the GitHub page):

var express    = require('express');
var bodyParser = require('body-parser');

var app = express();

app.use(bodyParser());

app.use(function (req, res, next) {
  console.log(req.body) // populated!
  next();
})

Update for Express 4.4.1

Middleware of the following is removed from Express.

• bodyParser
• json
• urlencoded
• multipart

When you use the middleware directly like you did in express 3.0. You will get the following error:

Error: Most middleware (like urlencoded) is no longer bundled with Express and 
must be installed separately.

In order to utilize those middleware, now you need to do npm for each middleware separately.

Since bodyParser is marked as deprecated, so I recommend the following way using json, urlencode and multipart parser like formidable, connect-multiparty. (Multipart middleware is deprecated as well).

Also remember, just defining urlencode + json, the form data will not be parsed and req.body will be undefined. You need to define a middleware handle the multipart request.

var urlencode = require('urlencode');
var json = require('json-middleware');
var multipart = require('connect-multiparty');
var multipartMiddleware = multipart();

app.use(json);
app.use(urlencode);
app.use('/url/that/accepts/form-data', multipartMiddleware);

This will do it if you want to build the posted query without middleware:

app.post("/register/",function(req,res){
    var bodyStr = '';
    req.on("data",function(chunk){
        bodyStr += chunk.toString();
    });
    req.on("end",function(){
        res.send(bodyStr);
    });

});

That will send this to the browser

email=emailval&password1=pass1val&password2=pass2val

It's probably better to use middleware though so you don't have to write this over and over in each route.

Request streaming worked for me

req.on('end', function() {
    var paramstring = postdata.split("&");
});

var postdata = "";
req.on('data', function(postdataChunk){
    postdata += postdataChunk;
});

For Express 4.1 and above

As most of the answers are using to Express, bodyParser, connect; where multipart is deprecated. There is a secure way to send post multipart objects easily.

Multer can be used as replacement for connect.multipart().

To install the package

$ npm install multer

Load it in your app:

var multer = require('multer');

And then, add it in the middleware stack along with the other form parsing middleware.

app.use(express.json());
app.use(express.urlencoded());
app.use(multer({ dest: './uploads/' }));

connect.json() handles application/json

connect.urlencoded() handles application/x-www-form-urlencoded

multer() handles multipart/form-data

Backend:

import express from 'express';
import bodyParser from 'body-parser';

const app = express();
app.use(bodyParser.json()); // add a middleware (so that express can parse request.body's json)

app.post('/api/courses', (request, response) => {
  response.json(request.body);
});

Frontend:

fetch("/api/courses", {
  method: 'POST',
  body: JSON.stringify({ hi: 'hello' }), // stringify JSON
  headers: new Headers({ "Content-Type": "application/json" }); // add headers
});

I could find all parameters by using following code for both POST and GET requests.

 var express = require('express');
    var app = express();
    const util = require('util');  
    app.post('/', function (req, res) {
        console.log("Got a POST request for the homepage");
        res.send(util.inspect(req.query,false,null));
    })

</div>

I was searching for this exact problem. I was following all the advice above but req.body was still returning an empty object {}. In my case, it was something just as simple as the html being incorrect.

In your form's html, make sure you use the 'name' attribute in your input tags, not just 'id'. Otherwise, nothing is parsed.

<input id='foo' type='text' value='1'/>             // req = {}
<input id='foo' type='text' name='foo' value='1' /> // req = {foo:1}

My idiot mistake is your benefit.

Post Parameters can be retrieved as follows-

app.post('/api/v1/test',Testfunction);
http.createServer(app).listen(port, function(){
console.log("Express server listening on port " + port)
});

function Testfunction(request,response,next)
{
   console.log(request.param("val1"));

   response.send('HI');
}

use express-fileupload package

var app = require('express')();
var http = require('http').Server(app);
const fileUpload = require('express-fileupload')

app.use(fileUpload());

app.post('/', function(req, res) {
var email = req.body.email;
res.send('<h1>Email :</h1> '+email);
});

http.listen(3000, function(){
  console.log('Running Port:3000');
});

var express        =         require("express");
var bodyParser     =         require("body-parser");
var app            =         express();

app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

app.get('/',function(req,res){
  res.sendfile("index.html");
});
app.post('/login',function(req,res){
  var user_name=req.body.user;
  var password=req.body.password;
  console.log("User name = "+user_name+", password is "+password);
  res.end("yes");
});
app.listen(3000,function(){
  console.log("Started on PORT 3000");
})

You are using 'req.query.post' with wrong method 'req.query.post' works with 'method=get' 'method=post' works with body-parser.

Just try this by changing post to get

<form id="loginformA" action="userlogin" method="get">
<div>
    <label for="email">Email: </label>
    <input type="text" id="email" name="email"></input>
</div>
<input type="submit" value="Submit"></input>  
</form>

And in express code use 'app.get'