Request and response formatting (JSON, XML)

In Express.js, it is easy to format the request and response in various formats including JSON and XML.

To format the request and response in JSON, we don't need to do anything as Express.js automatically parses the request body as JSON if the request header's content-type is set to application/json. We can simply use res.json() method to send the response in JSON format.

Here's an example:

const express = require('express');
const app = express();

app.use(express.json()); // to parse incoming requests with JSON payloads

app.get('/users', (req, res) => {
  const users = [
    { id: 1, name: 'John Doe', email: 'john.doe@example.com' },
    { id: 2, name: 'Jane Doe', email: 'jane.doe@example.com' },
  ];

  res.json(users); // send response in JSON format
});

app.listen(3000, () => console.log('Server started on port 3000'));

To format the response in XML, we can use a package like xmlbuilder or xml2js. Here's an example using xmlbuilder:

const express = require('express');
const xmlbuilder = require('xmlbuilder');

const app = express();

app.get('/users', (req, res) => {
  const users = [
    { id: 1, name: 'John Doe', email: 'john.doe@example.com' },
    { id: 2, name: 'Jane Doe', email: 'jane.doe@example.com' },
  ];

  const xml = xmlbuilder.create('users');
  users.forEach(user => {
    xml.ele('user', { id: user.id })
      .ele('name', user.name).up()
      .ele('email', user.email).up()
      .up();
  });

  res.set('Content-Type', 'application/xml');
  res.send(xml.toString()); // send response in XML format
});

app.listen(3000, () => console.log('Server started on port 3000'));

In this example, we're using xmlbuilder to create an XML document with the users root element and user child elements for each user. We then set the content-type header to application/xml and send the XML document as the response.