Hello world example

以下に埋め込まれているのは、基本的に作成できる最も簡単なExpressアプリです。以下に埋め込まれているのは、基本的に作成できる最も簡単なExpressアプリです。 It is a single file app — not what you’d get if you use the Express generator, which creates the scaffolding for a full app with numerous JavaScript files, Jade templates, and sub-directories for various purposes.

const express = require('express');
const app = express();
const port = 3000;

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

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

import express from 'express';

const app = express();
const port = 3000;

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

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

import express, { type Express, type Request, type Response } from 'express';

const app: Express = express();
const port = 3000;

app.get('/', (req: Request, res: Response) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

This app starts a server and listens on port 3000 for connections. The app responds with “Hello World!” for requests to the root URL (/) or route. For every other path, it will respond with a 404 Not Found.

ローカルで実行中

最初に myapp という名前のディレクトリを作成し、変更して npm init を実行します。 Then, install express as a dependency, as per the installation guide. Then, install express as a dependency, as per the installation guide.

myapp ディレクトリで、app.jsという名前のファイルを作成し、上の例からコードをコピーします。

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.

次のコマンドでアプリを実行します。

$ node app.js

次に、ブラウザーに http://localhost:3000/ をロードして出力を確認します。