Express.js res上的常用方法

本文介绍在使用express框架时，res对象上11种常用方法的使用结合代码分别做了介绍。

1. res.send([body])

• 功能 : 发送各种类型的数据响应，如Buffer、String、Object或Array。Express会根据响应类型自动分配正确的内容类型。

• 示例 :

  app.get('/', (req, res) => {
    res.send('<h1>你好，世界</h1>'); // 发送text/html响应
  });

2. res.json([body])

• 功能 : 发送JSON响应。这个方法类似于res.send()，但始终将非Buffer对象转换为JSON字符串后再发送。

• 示例 :

  app.get('/user', (req, res) => {
    res.json({ name: '爱丽丝', age: 25 }); // 自动设置内容类型为application/json
  });

3. res.end([data[, encoding]])

• 功能: 结束响应过程。当不需要向客户端发送更多数据时使用此方法。

• 示例 :

  app.get('/stream', (req, res) => {
    res.write('数据的第一部分 ');
    res.end('数据的最后部分'); // 结束响应，可以发送或不发送数据
  });

4. res.status(code)

• 功能: 设置响应的HTTP状态码。

• 示例 :

  app.get('/not-found', (req, res) => {
    res.status(404).send('未找到'); // 可与其他res方法链式调用
  });

5. res.sendFile(path [, options] [, fn])

• 功能: 传输给定路径的文件。根据文件扩展名设置响应的Content-Type HTTP头字段。

• 示例 :

  app.get('/download', (req, res) => {
    const filePath = __dirname + '/files/document.pdf';
    res.sendFile(filePath); // 自动设置内容处置为附件
  });

6. res.render(view [, locals] [, callback])

• 功能: 渲染视图并将渲染的HTML字符串发送到客户端。通常与模板引擎一起使用。

• 示例 :

  app.get('/dashboard', (req, res) => {
    res.render('dashboard', { user: '爱丽丝' }); // 渲染带有用户数据的'dashboard'视图
  });

7. res.redirect([status,] path)

• 功能: 重定向到由指定路径派生的URL，可选状态码。

• 示例 :

  app.get('/old-page', (req, res) => {
    res.redirect(301, '/new-page'); // 301永久移动状态码
  });

8. res.set(field [, value])

• 功能 : 将响应的HTTP头 field 设置为 value。也可以传递一个对象以设置多个字段。

• 示例 :

  app.get('/with-headers', (req, res) => {
    res.set({
      'Content-Type': 'application/json',
      'Custom-Header': 'HeaderValue'
    });
    res.send({ message: '头部设置' });
  });

9. res.cookie(name, value [, options])

• 功能 : 设置名为 name 的cookie的值，附带一个选项对象。

• 示例 :

  app.get('/set-cookie', (req, res) => {
    res.cookie('session_id', '12345', { maxAge: 900000, httpOnly: true });
    res.send('Cookie已设置');
  });

10. res.clearCookie(name [, options])

• 功能: 清除指定名字的cookie。

• 示例 :

  app.get('/clear-cookie', (req, res) => {
    res.clearCookie('session_id');
    res.send('Cookie已清除');
  });

11. res.type(type)

• 功能 : 将Content-Type HTTP头设置为由type确定的MIME类型。

• 示例 :

  app.get('/text', (req, res) => {
    res.type('txt').send('文本响应'); // 设置内容类型为text/plain
  });

---

English version: Expanded and Detailed Explanation of Express.js res Methods

1. res.send([body])

• Functionality : Sends a response with various types of data, such as a Buffer, String, an Object, or an Array. Express automatically assigns the correct content-type based on the type of the response.

• Example :

  app.get('/', (req, res) => {
    res.send('<h1>Hello World</h1>'); // Sends a text/html response
  });

2. res.json([body])

• Functionality : Sends a JSON response. This method is similar to res.send() but always converts non-Buffer objects into JSON strings before sending them.

• Example :

  app.get('/user', (req, res) => {
    res.json({ name: 'Alice', age: 25 }); // Automatically sets Content-Type to application/json
  });

3. res.end([data[, encoding]])

• Functionality: Ends the response process. This method is used when no more data needs to be sent to the client.

• Example :

  app.get('/stream', (req, res) => {
    res.write('Part 1 of the data ');
    res.end('Final part of the data'); // Ends the response with or without sending data
  });

4. res.status(code)

• Functionality: Sets the HTTP status code of the response.

• Example :

  app.get('/not-found', (req, res) => {
    res.status(404).send('404 Not Found'); // Chainable with other res methods
  });

5. res.sendFile(path [, options] [, fn])

• Functionality: Transfers the file at the given path. Sets the Content-Type response HTTP header field based on the file's extension.

• Example :

  app.get('/download', (req, res) => {
    const filePath = __dirname + '/files/document.pdf';
    res.sendFile(filePath); // Automatically sets Content-Disposition for attachment
  });

6. res.render(view [, locals] [, callback])

• Functionality: Renders a view and sends the rendered HTML string to the client. Typically used with template engines.

• Example :

  app.get('/dashboard', (req, res) => {
    res.render('dashboard', { user: 'Alice' }); // Renders 'dashboard' view with the user data
  });

7. res.redirect([status,] path)

• Functionality: Redirects to the URL derived from the specified path, with optional status code.

• Example :

  app.get('/old-page', (req, res) => {
    res.redirect(301, '/new-page'); // 301 Moved Permanently status code
  });

8. res.set(field [, value])

• Functionality : Sets the response's HTTP header field to value. Can also pass an object to set multiple fields.

• Example :

  app.get('/with-headers', (req, res) => {
    res.set({
      'Content-Type': 'application/json',
      'Custom-Header': 'HeaderValue'
    });
    res.send({ message: 'Headers set' });
  });

9. res.cookie(name, value [, options])

• Functionality : Sets cookie name to value, with an options object.

• Example :

  app.get('/set-cookie', (req, res) => {
    res.cookie('session_id', '12345', { maxAge: 900000, httpOnly: true });
    res.send('Cookie set');
  });

10. res.clearCookie(name [, options])

• Functionality : Clears the cookie specified by name.

• Example :

  app.get('/clear-cookie', (req, res) => {
    res.clearCookie('session_id');
    res.send('Cookie cleared');
  });

11. res.type(type)

• Functionality : Sets the Content-Type HTTP header to the MIME type as determined by type.

• Example :

  app.get('/text', (req, res) => {
    res.type('txt').send('Text response'); // Sets Content-Type to text/plain
  });
  ``