req.body empty on posts

I discovered, that it works when sending with content type

"application/json"

in combination with server-side
app.use(express.json())
(As @marcelocra pointed out, the 2022 version would use)

(old version for reference)
app.use(bodyParser.json());

Now I can send via

var data = {name:"John"}
var xmlHttp = new XMLHttpRequest();
xmlHttp.open("POST", theUrl, false); // false for synchronous request
xmlHttp.setRequestHeader("Content-type", "application/json");
xmlHttp.send(data);

and the result is available in request.body.name on the server.

In Postman of the 3 options available for content type select "X-www-form-urlencoded" and it should work.

Also to get rid of error message replace:

app.use(bodyParser.urlencoded())

With:

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

See https://github.com/expressjs/body-parser

The 'body-parser' middleware only handles JSON and urlencoded data, not multipart

As @SujeetAgrahari mentioned, body-parser is now inbuilt with express.js.

Use app.use(express.json()); to implement it in recent versions for JSON bodies. For URL encoded bodies (the kind produced by HTTP form POSTs) use app.use(express.urlencoded());

With Postman, to test HTTP post actions with a raw JSON data payload, select the raw option and set the following header parameters:

Content-Type: application/json

Also, be sure to wrap any strings used as keys/values in your JSON payload in double quotes.

The body-parser package will parse multi-line raw JSON payloads just fine.

{
    "foo": "bar"
}

Tested in Chrome v37 and v41 with the Postman v0.8.4.13 extension (body-parser v1.12.2 and express v4.12.3) with the setup below:

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

// configure the app to use bodyParser()
app.use(bodyParser.urlencoded({
    extended: true
}));
app.use(bodyParser.json());

// ... Your routes and methods here