Express: send() vs json() vs end()

README.md

Express: res.send() vs res.json() vs res.end()

Materials

• Article res.json() vs res.send() vs res.end() in Express
• MDN: Common MIME types

Key Takeaways

• When in doubt, use .send(). It dynamically sets Content-Type headers to match the data it sends.
• When sending JSON, you can either use .json() or .send().
  • .json() is likely less confusing
  • .json() uses .send() under the hood so the resulting HTTP headers are the same.
• .json() has JSON formatting options (replacer and space) that you'll probably never need.
• Only use .end() when you need to end the response without providing data.
  • .send()/.json() will end the response after they send data anyway.

server.js

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

/***********/
/* .send() */
/***********/

// Text -> text/html
app.get('/send/text',(req, res) => {
  res.send('hello world');
});

// HTML -> text/html
app.get('/send/html',(req, res) => {
  res.send('<p>hello world</p>');
});

// JSON -> application/json
app.get('/send/json',(req, res) => {
  res.send({hello: 'world'});
});

/***********/
/* .json() */
/***********/

// JSON -> application/json
app.get('/json/json',(req, res) => {
  res.json({hello: 'world'});
})
// HTML -> application/json  -- this is strange
app.get('/json/html',(req, res) => {
  res.json('<p>hello world</p>');
})

/***********/
/* .end() */
/***********/

// Text --> No `Content-Type`  -- strange
app.get('/end/text',(req, res) => {
  res.end('hello world');
});

// HTML --> No `Content-Type`  -- strange, don't do this
app.get('/end/html',(req, res) => {
  res.end('<p>hello world</p>');
});

// JSON --> text/html  -- strange, don't do this
app.get('/end/json',(req, res) => {
  res.end({hello: 'world'});
});

const PORT = process.env.PORT || 4000
app.listen(PORT, function(){
  console.log(`Listening on port ${PORT}.`)
})