Express Response Object

The response object, abbreviated as res, gives you methods to send a response back to the client. You call one of these methods at the end of every route handler.

Response methods

res.send(): send any data (text, HTML, or an object)
res.json(): send a JSON response
res.status(): set the HTTP status code (chainable)
res.redirect(): redirect to a different path
res.render(): render a view template
res.sendFile(): send a file

res.send()

Sends a response with any content type. Express detects the type automatically.

app.get('/', (req, res) => {
  res.send({ people: ['Anna', 'John'] }); // sends JSON
  res.send('<h1>Hello World</h1>');        // sends HTML
  res.send('Normal text');                 // sends plain text
});

res.json()

Sends a JSON response and sets the Content-Type header to application/json. Prefer this over res.send() when returning JSON from an API.

app.get('/api/users', (req, res) => {
  res.json({ people: ['Anna', 'John'] });
});

res.status()

Sets the HTTP status code. It is chainable, so you can combine it with res.json() or res.send():

app.get('/not-found', (req, res) => {
  res.status(404).json({ error: 'Not found' });
});

app.get('/error', (req, res) => {
  res.status(500).send('Internal server error');
});

Status code ranges:

1xx: informational
2xx: success
3xx: redirects
4xx: client errors
5xx: server errors

res.redirect()

Redirects the client to a different URL. Express sets the status code automatically (302 by default):

app.get('/old-path', (req, res) => {
  res.redirect('/new-path');
});

res.render()

Renders a view template and sends the resulting HTML. Requires a view engine to be set up. See View Engines for details.

res.sendFile()

Sends a file. By default it requires an absolute path, so pass { root: __dirname } for relative paths:

app.get('/', (req, res) => {
  res.sendFile('./views/index.html', { root: __dirname });
});

Practical examples

Sending simple HTML

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

app.listen(3000);

app.get('/', (req, res) => {
  res.send('<p>Home page</p>');
});

app.get('/about', (req, res) => {
  res.send('<p>About page</p>');
});

Sending HTML files

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

app.listen(3000);

app.get('/', (req, res) => {
  res.sendFile('./views/index.html', { root: __dirname });
});

app.get('/about', (req, res) => {
  res.sendFile('./views/about.html', { root: __dirname });
});

Redirects and 404

// Redirect /about-us to /about
app.get('/about-us', (req, res) => {
  res.redirect('/about');
});

// 404 handler: must be last, after all other routes
app.use((req, res) => {
  res.status(404).sendFile('./views/404.html', { root: __dirname });
});