このドキュメントは、英語でのドキュメントへの時代遅れの相対的な可能性があります。最新の更新プログラムのために、英語でのドキュメントを参照してください。

This document might be outdated relative to the documentation in English. For the latest updates, please refer the documentation in English.

✖

Hello world example

Here is an example of a very basic Express app.

var express = require('express')
var app = express()

app.get('/', function (req, res) {
  res.send('Hello World!')
})

var server = app.listen(3000, function () {

  var host = server.address().address
  var port = server.address().port

  console.log('Example app listening at http://%s:%s', host, port)

})

The req (request) and res (response) are the exact same objects that Node provides, so you can invoke req.pipe(), req.on('data', callback) and anything else you would do without Express involved.

The app starts a server and listens on port 3000 for connection. It will respond with “Hello World!” for requests to the homepage. For every other path, it will respond with a 404 Not Found.

Save the code in a file named app.js and run it with the following command.

$ node app.js

Then, load http://localhost:3000/ in a browser to see the output.