Express.js req上的常用方法

在 Express.js 中，request 对象（通常称为 req）代表 HTTP 请求，具有请求查询字符串、参数、正文、HTTP 头等的属性。本文介绍 req 对象的一些关键属性和方法。

1. req.params

• 功能 : 包含映射到命名路由参数的属性的对象。例如，如果您有路由 /user/:name，则可以通过 req.params.name 访问 name 属性。

• 示例 :

  app.get('/user/:name', (req, res) => {
    res.send(`你好, ${req.params.name}`);
  });

2. req.query

• 功能 : 包含路由中每个查询字符串参数的属性的对象。如果查询字符串为 ?name=John&age=30，req.query 将是 { name: 'John', age: '30' }。

• 示例 :

  app.get('/search', (req, res) => {
    const { name, age } = req.query;
    res.send(`搜索结果：${name}，年龄 ${age}`);
  });

3. req.body

• 功能 : 包含请求正文中提交的键值对。默认情况下，它是 undefined，当您使用诸如 express.json() 或 express.urlencoded() 之类的解析中间件时，它会被填充。

• 示例 :

  app.post('/login', express.json(), (req, res) => {
    const { username, password } = req.body;
    res.send(`正在登录 ${username}`);
  });

4. req.headers

• 功能 : 包含请求的 HTTP 头的对象。例如，req.headers['content-type'] 将给出请求的内容类型。

• 示例 :

  app.get('/api', (req, res) => {
    const contentType = req.headers['content-type'];
    res.send(`内容类型是 ${contentType}`);
  });

5. req.method

• 功能: 表示请求的 HTTP 方法的字符串：GET、POST、PUT、DELETE 等。

• 示例 :

  app.use((req, res, next) => {
    console.log(`收到一个 ${req.method} 请求`);
    next();
  });

6. req.url 或 req.originalUrl

• 功能 : req.url 提供 URL 的路径部分，而 req.originalUrl 提供完整的原始 URL。

• 示例 :

  app.use((req, res, next) => {
    console.log(`原始 URL: ${req.originalUrl}`);
    next();
  });

7. req.path

• 功能: 包含请求 URL 的路径部分。

• 示例 :

  app.get('/example', (req, res) => {
    console.log(`路径: ${req.path}`);
    res.send('路径示例');
  });

8. req.cookies

• 功能 : 包含请求发送的 cookies 的对象。需要使用 cookie-parser 中间件。

• 示例 :

  app.use(cookieParser());
  app.get('/', (req, res) => {
    console.log('Cookies: ', req.cookies);
    res.send('已接收 Cookie 数据');
  });

9. req.hostname

• 功能 : 包含从 Host HTTP 头派生的主机名。

• 示例 :

  app.get('/host', (req, res) => {
    res.send(`主机名: ${req.hostname}`);
  });

10. req.ip

• 功能: 包含请求的远程 IP 地址。

• 示例 :

  app.use((req, res, next) => {
    console.log(`IP 地址: ${req.ip}`);
    next();
  });

11. req.protocol

• 功能: 包含请求协议字符串：http 或 https（对于 TLS 请求）。

• 示例 :

  app.get('/protocol', (req, res) => {
    res.send(`协议: ${req.protocol}`);
  });

12. req.secure

• 功能: 如果建立了 TLS 连接，则为 true 的布尔属性。

• 示例 :

  app.get('/secure', (req, res) => {
    res.send(`是否安全: ${req.secure}`);
  });

这些 req 对象的属性和方法对于处理 Express.js 应用程序中的传入请求至关重要，使您能够访问请求参数、头部和正文内容等。

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English version

In Express.js, the request object (commonly referred to as req) represents the HTTP request and has properties for the request query string, parameters, body, HTTP headers, and more. Let's dive into some of the key properties and methods of the req object, along with explanations and code examples:

1. req.params

• Functionality : An object containing properties mapped to the named route parameters. For example, if you have the route /user/:name, then the name property is available as req.params.name.

• Example :

  app.get('/user/:name', (req, res) => {
    res.send(`Hello, ${req.params.name}`);
  });

2. req.query

• Functionality : An object containing a property for each query string parameter in the route. If there is a query string ?name=John&age=30, req.query would be { name: 'John', age: '30' }.

• Example :

  app.get('/search', (req, res) => {
    const { name, age } = req.query;
    res.send(`Search results for ${name} aged ${age}`);
  });

3. req.body

• Functionality : Contains key-value pairs of data submitted in the request body. By default, it is undefined, and is populated when you use body-parsing middleware such as express.json() or express.urlencoded().

• Example :

  app.post('/login', express.json(), (req, res) => {
    const { username, password } = req.body;
    res.send(`Logging in ${username}`);
  });

4. req.headers

• Functionality : An object containing the request's HTTP headers. For example, req.headers['content-type'] will give you the content type of the request.

• Example :

  app.get('/api', (req, res) => {
    const contentType = req.headers['content-type'];
    res.send(`Content-Type is ${contentType}`);
  });

5. req.method

• Functionality: A string representing the HTTP method of the request: GET, POST, PUT, DELETE, etc.

• Example :

  app.use((req, res, next) => {
    console.log(`Received a ${req.method} request`);
    next();
  });

6. req.url or req.originalUrl

• Functionality : req.url provides the path part of the URL, whereas req.originalUrl provides the full original URL.

• Example :

  app.use((req, res, next) => {
    console.log(`Original URL: ${req.originalUrl}`);
    next();
  });

7. req.path

• Functionality: Contains the path part of the request URL.

• Example :

  app.get('/example', (req, res) => {
    console.log(`Path: ${req.path}`);
    res.send('Path example');
  });

8. req.cookies

• Functionality : An object containing the cookies sent by the request. Requires the cookie-parser middleware to be used.

• Example :

  app.use(cookieParser());
  app.get('/', (req, res) => {
    console.log('Cookies: ', req.cookies);
    res.send('Cookie data received');
  });

9. req.hostname

• Functionality : Contains the hostname derived from the Host HTTP header.

• Example :

  app.get('/host', (req, res) => {
    res.send(`Hostname: ${req.hostname}`);
  });

10. req.ip

• Functionality: Contains the remote IP address of the request.

• Example :

  app.use((req, res, next) => {
    console.log(`IP address: ${req.ip}`);
    next();
  });

11. req.protocol

• Functionality: Contains the request protocol string: either http or (for TLS requests) https.

• Example :

  app.get('/protocol', (req, res) => {
    res.send(`Protocol: ${req.protocol}`);
  });

12. req.secure

• Functionality: A Boolean property that is true if a TLS connection is established.

• Example :

  app.get('/secure', (req, res) => {}`);
  });

These properties and methods of the req object are essential for handling incoming requests in an Express.js application, allowing you to access request parameters, headers, and body content, among other things.