How to access the request body when POSTing using Node.js and Express?

I have the following Node.js code:

var express = require('express');
var app = express.createServer(express.logger());
app.use(express.bodyParser());

app.post('/', function(request, response) {
    response.write(request.body.user);
    response.end();
});

Now if I POST something like:

curl -d user=Someone -H Accept:application/json --url http://localhost:5000

I get Someone as expected. Now, what if I want to get the full request body? I tried doing response.write(request.body) but Node.js throws an exception saying "first argument must be a string or Buffer" then goes to an "infinite loop" with an exception that says "Can't set headers after they are sent."; this also true even if I did var reqBody = request.body; and then writing response.write(reqBody).

What's the issue here?

Also, can I just get the raw request without using express.bodyParser()?

Starting from express v4.16 there is no need to require any additional modules, just use the built-in JSON middleware:

app.use(express.json())

Like this:

const express = require('express')

app.use(express.json())    // <==== parse request body as JSON

app.listen(8080)

app.post('/test', (req, res) => {
  res.json({requestBody: req.body})  // <==== req.body will be a parsed JSON object
})

Note - body-parser, on which this depends, is already included with express.

Also don't forget to send the header Content-Type: application/json

Express 4.0 and above:

$ npm install --save body-parser

And then in your node app:

const bodyParser = require('body-parser');
app.use(bodyParser);

Express 3.0 and below:

Try passing this in your cURL call:

--header "Content-Type: application/json"

and making sure your data is in JSON format:

{"user":"someone"}

Also, you can use console.dir in your node.js code to see the data inside the object as in the following example:

var express = require('express');
var app = express.createServer();

app.use(express.bodyParser());

app.post('/', function(req, res){
    console.dir(req.body);
    res.send("test");
}); 

app.listen(3000);

This other question might also help: How to receive JSON in express node.js POST request?

If you don't want to use the bodyParser check out this other question: https://stackoverflow.com/a/9920700/446681

As of Express 4, the following code appears to do the trick. Note that you'll need to install body-parser using npm.

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
app.use(bodyParser.urlencoded({ extended: false }));


app.listen(8888);

app.post('/update', function(req, res) {
    console.log(req.body); // the posted data
});

For 2019, you don't need to install body-parser.

You can use:

var express = require('express');
var app = express();
app.use(express.json())
app.use(express.urlencoded({extended: true}))
app.listen(8888);
app.post('/update', function(req, res) {
    console.log(req.body); // the posted data
});

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json())

var port = 9000;

app.post('/post/data', function(req, res) {
    console.log('receiving data...');
    console.log('body is ',req.body);
    res.send(req.body);
});

// start the server
app.listen(port);
console.log('Server started! At http://localhost:' + port);

This will help you. I assume you are sending body in json.