expressjs.com/zh-cn/starter/hello-world.md

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layout	title	description	menu	order	redirect_from
page	Express“Hello World”示例	Get started with Express.js by building a simple 'Hello World' application, demonstrating the basic setup and server creation for beginners.	starter	2

Hello world 示例

Embedded below is essentially the simplest Express app you can create. It is a single file app — _not_ what you'd get if you use the [Express generator](/{{ page.lang }}/starter/generator.html), 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}`)
})

This app starts a server and listens on port 3000 for connections. 应用程序会启动服务器，并在端口 3000 上侦听连接。此应用程序以“Hello World!”响应针对根 URL (/) 或_路由_的请求。对于其他所有路径，它将以 404 Not Found 进行响应。 For every other path, it will respond with a 404 Not Found.

Running Locally

首先创建名为 myapp 的目录，切换到此目录，然后运行 npm init。根据[安装指南](/{{ page.lang }}/starter/installing.html)将 express 安装为依赖项。 Then, install express as a dependency, as per the [installation guide](/{{ page.lang }}/starter/installing.html).

在 myapp 目录中，创建名为 app.js 的文件，然后添加以下代码：

`req`（请求）和 `res`（响应）与 Node 提供的对象完全相同，所以您可以在不涉及 Express 的情况下调用 `req.pipe()`、`req.on('data', callback)` 和要执行的其他任何函数。

使用以下命令运行应用程序：

$ node app.js

然后，在浏览器中输入 http://localhost:3000/ 以查看输出。