5.x API

express.json([options])

This is a built-in middleware function in Express. 这是Express中内置的中间件功能。It parses incoming requests with JSON payloads and is based on body-parser.它使用JSON有效载荷解析传入的请求，并基于body-parser。

Returns middleware that only parses JSON and only looks at requests where the Content-Type header matches the type option. 返回只解析JSON并且只查看Content-Type标头与type选项匹配的请求的中间件。This parser accepts any Unicode encoding of the body and supports automatic inflation of gzip and deflate encodings.此解析器接受正文的任何Unicode编码，并支持gzip和deflate编码的自动膨胀。

A new body object containing the parsed data is populated on the request object after the middleware (i.e. req.body), or undefined if there was no body to parse, the Content-Type was not matched, or an error occurred.在中间件之后，在request对象上填充包含解析数据的新body对象（即req.body），或者如果没有要解析的主体、Content-Type不匹配或发生错误，则填充undefined的主体对象。

The following table describes the properties of the optional options object.下表描述了可选options对象的属性。

express.raw([options])

This is a built-in middleware function in Express. 这是Express中内置的中间件功能。It parses incoming request payloads into a Buffer and is based on body-parser.它将传入的请求有效载荷解析到Buffer中，并基于body-parser。

Returns middleware that parses all bodies as a Buffer and only looks at requests where the Content-Type header matches the type option. 返回中间件，该中间件将所有主体解析为Buffer，并且只在Content-Type标头与Type选项匹配的情况下查看请求。This parser accepts any Unicode encoding of the body and supports automatic inflation of gzip and deflate encodings.此解析器接受正文的任何Unicode编码，并支持gzip和deflate编码的自动膨胀。

A new body Buffer containing the parsed data is populated on the request object after the middleware (i.e. req.body), or undefined if there was no body to parse, the Content-Type was not matched, or an error occurred.在中间件（即req.body）之后，在request对象上填充包含解析数据的新body Buffer，或者如果没有要解析的主体、内容类型不匹配或发生错误，则填充undefined的主体缓冲区。

The following table describes the properties of the optional options object.下表描述了可选options对象的属性。

express.Router([options])

Creates a new router object.创建新的router对象。

const router = express.Router([options])

The optional options parameter specifies the behavior of the router.可选options参数指定路由器的行为。

You can add middleware and HTTP method routes (such as get, put, post, and so on) to router just like an application.您可以像应用程序一样向路由器添加中间件和HTTP方法路由（如get、put、post等）。

For more information, see Router.有关更多信息，请参阅Router。

express.static(root, [options])

This is a built-in middleware function in Express.这是Express中内置的中间件功能。 It serves static files and is based on serve-static.它提供静态文件，基于serve-static。

The root argument specifies the root directory from which to serve static assets.root参数指定从中提供静态资产的根目录。 The function determines the file to serve by combining req.url with the provided root directory.该函数通过将req.url与提供的根目录组合来确定要服务的文件。 When a file is not found, instead of sending a 404 response, it instead calls next() to move on to the next middleware, allowing for stacking and fall-backs.当找不到文件时，它不是发送404响应，而是调用next()继续下一个中间件，允许堆叠和回退。

The following table describes the properties of the options object.下表描述了options对象的属性。 See also the example below.另请参阅下面的示例。

For more information, see Serving static files in Express.有关更多信息，请参阅在Express中提供静态文件， and Using middleware - Built-in middleware.以及使用中间件——内置中间件。

dotfiles

Possible values for this option are:此选项的可能值为：

• “allow” - No special treatment for dotfiles.对点档案没有特殊处理。
• “deny” - Deny a request for a dotfile, respond with 403, then call next().拒绝对点文件的请求，返回403，然后调用next()。
• “ignore” - Act as if the dotfile does not exist, respond with 404, then call next().假设点文件不存在，用404响应，然后调用next()。

fallthrough

When this option is true, client errors such as a bad request or a request to a non-existent file will cause this middleware to simply call next() to invoke the next middleware in the stack.当此选项为true时，客户端错误（如错误的请求或对不存在的文件的请求）将导致此中间件简单地调用next()来调用堆栈中的下一个中间件。 When false, these errors (even 404s), will invoke next(err).当为false时，这些错误（甚至404）将调用next(err)。

Set this option to true so you can map multiple physical directories to the same web address or for routes to fill in non-existent files.将此选项设置为true，以便您可以将多个物理目录映射到同一网址，或用于路由以填充不存在的文件。

Use false if you have mounted this middleware at a path designed to be strictly a single file system directory, which allows for short-circuiting 404s for less overhead. This middleware will also reply to all methods.如果您将此中间件安装在严格设计为单个文件系统目录的路径上，则使用false，这允许短路404以减少开销。此中间件还将回复所有方法。

setHeaders

For this option, specify a function to set custom response headers. Alterations to the headers must occur synchronously.对于此选项，指定一个函数来设置自定义响应标头。标题的更改必须同步进行。

The signature of the function is:函数的签名为：

fn(res, path, stat)

Arguments:论据：

• res, the response object.，即响应对象。
• path, the file path that is being sent.，正在发送的文件路径。
• stat, the stat object of the file that is being sent.，正在发送的文件的stat对象。

Example of express.staticexpress.static的示例

Here is an example of using the express.static middleware function with an elaborate options object:下面是一个使用express.static中间件函数和一个精心设计的选项对象的示例：

const options = {
  dotfiles: 'ignore',
  etag: false,
  extensions: ['htm', 'html'],
  index: false,
  maxAge: '1d',
  redirect: false,
  setHeaders (res, path, stat) {
    res.set('x-timestamp', Date.now())
  }
}

app.use(express.static('public', options))

express.text([options])

This is a built-in middleware function in Express. It parses incoming request payloads into a string and is based on body-parser.这是Express中内置的中间件功能。它将传入的请求有效载荷解析为字符串，并基于body-parser。

Returns middleware that parses all bodies as a string and only looks at requests where the Content-Type header matches the type option. 返回中间件，该中间件将所有主体解析为字符串，并且只在Content-Type标头与type选项匹配的情况下查看请求。This parser accepts any Unicode encoding of the body and supports automatic inflation of gzip and deflate encodings.此解析器接受正文的任何Unicode编码，并支持gzip和deflate编码的自动膨胀。

A new body string containing the parsed data is populated on the request object after the middleware (i.e. req.body), or undefined if there was no body to parse, the Content-Type was not matched, or an error occurred.在中间件之后，在请求对象上填充包含解析数据的新body字符串（即req.body），或者如果没有要解析的正文、Content-Type不匹配或发生错误，则填充undefined的正文字符串。

The following table describes the properties of the optional options object.下表描述了可选options对象的属性。

express.urlencoded([options])

This is a built-in middleware function in Express. It parses incoming requests with urlencoded payloads and is based on body-parser.这是Express中内置的中间件功能。它使用url编码的有效载荷解析传入的请求，并基于body-parser。

Returns middleware that only parses urlencoded bodies and only looks at requests where the Content-Type header matches the type option. 返回的中间件仅解析url编码的主体，并且只查找Content-Type标头与类型选项匹配的请求。This parser accepts only UTF-8 encoding of the body and supports automatic inflation of gzip and deflate encodings.此解析器只接受正文的UTF-8编码，并支持gzip和deflate编码的自动膨胀。

A new body object containing the parsed data is populated on the request object after the middleware (i.e. req.body), or undefined if there was no body to parse, the Content-Type was not matched, or an error occurred. 在中间件之后，在request对象上填充包含解析数据的新body对象（即req.body），或者如果没有要解析的主体、内容类型不匹配或发生错误，则填充 undefined主体对象。This object will contain key-value pairs, where the value can be a string or array (when extended is false), or any type (when extended is true).此对象将包含键值对，其中值可以是字符串或数组（当extended为false时），也可以是任何类型（当extended为true时）。

The following table describes the properties of the optional options object.下表描述了可选options对象的属性。

app.locals

The app.locals object has properties that are local variables within the application, and will be available in templates rendered with res.render.app.locals对象的属性是应用程序中的局部变量，将在使用res.render渲染的模板中可用。

console.dir(app.locals.title)
// => 'My App'

console.dir(app.locals.email)
// => '[email protected]'

Once set, the value of app.locals properties persist throughout the life of the application, in contrast with res.locals properties that are valid only for the lifetime of the request.一旦设置，app.locals属性的值将在应用程序的整个生命周期内持续存在，而res.locals属性仅在请求的生命周期内有效。

You can access local variables in templates rendered within the application.您可以访问应用程序中呈现的模板中的局部变量。 This is useful for providing helper functions to templates, as well as application-level data.这对于为模板提供辅助函数以及应用程序级数据非常有用。 Local variables are available in middleware via req.app.locals (see req.app)局部变量可以通过req.app.locals在中间件中使用（请参阅req.app）

app.locals.title = 'My App'
app.locals.strftime = require('strftime')
app.locals.email = '[email protected]'

app.mountpath

The app.mountpath property contains one or more path patterns on which a sub-app was mounted.app.mountpath属性包含一个或多个子应用程序挂载的路径模式。

const express = require('express')

const app = express() // the main app
const admin = express() // the sub app

admin.get('/', (req, res) => {
  console.log(admin.mountpath) // /admin
  res.send('Admin Homepage')
})

app.use('/admin', admin) // mount the sub app

It is similar to the baseUrl property of the req object, except req.baseUrl returns the matched URL path, instead of the matched patterns.它类似于req对象的baseUrl属性，除了req.baseUrl返回匹配的URL路径，而不是匹配的模式。

If a sub-app is mounted on multiple path patterns, app.mountpath returns the list of patterns it is mounted on, as shown in the following example.如果一个子应用程序被挂载在多个路径模式上，app.mountpath会返回它所挂载的模式列表，如下例所示。

const admin = express()

admin.get('/', (req, res) => {
  console.log(admin.mountpath) // [ '/adm{*splat}n', '/manager' ]
  res.send('Admin Homepage')
})

const secret = express()
secret.get('/', (req, res) => {
  console.log(secret.mountpath) // /secr{*splat}t
  res.send('Admin Secret')
})

admin.use('/secr{*splat}t', secret) // load the 'secret' router on '/secr{*splat}t', on the 'admin' sub app
app.use(['/adm{*splat}n', '/manager'], admin) // load the 'admin' router on '/adm{*splat}n' and '/manager', on the parent app

app.router

The application’s in-built instance of router. This is created lazily, on first access.该应用程序是路由器的内置实例。这是在首次访问时缓慢创建的。

const express = require('express')
const app = express()
const router = app.router

router.get('/', (req, res) => {
  res.send('hello world')
})

app.listen(3000)

You can add middleware and HTTP method routes to the router just like an application.您可以像应用程序一样向router添加中间件和HTTP方法路由。

For more information, see Router.有关更多信息，请参阅Router。

app.on('mount', callback(parent))

The mount event is fired on a sub-app, when it is mounted on a parent app. The parent app is passed to the callback function.当子应用被挂载到父应用时，mount事件会在子应用上触发。父应用程序被传递给回调函数。

const admin = express()

admin.on('mount', (parent) => {
  console.log('Admin Mounted')
  console.log(parent) // refers to the parent app
})

admin.get('/', (req, res) => {
  res.send('Admin Homepage')
})

app.use('/admin', admin)

app.all(path, callback [, callback ...])

This method is like the standard app.METHOD() methods, except it matches all HTTP verbs.此方法类似于标准的app.METHOD()方法，只是它匹配所有HTTP谓词。

Arguments参数

Examples示例

The following callback is executed for requests to /secret whether using GET, POST, PUT, DELETE, or any other HTTP request method:无论是使用GET、POST、PUT、DELETE还是任何其他HTTP请求方法，都会对/secret的请求执行以下回调：

app.all('/secret', (req, res, next) => {
  console.log('Accessing the secret section ...')
  next() // pass control to the next handler
})

The app.all() method is useful for mapping “global” logic for specific path prefixes or arbitrary matches. For example, if you put the following at the top of all other route definitions, it requires that all routes from that point on require authentication, and automatically load a user. app.all()方法对于映射特定路径前缀或任意匹配的“全局”逻辑非常有用。例如，如果将以下内容放在所有其他路由定义的顶部，则要求从该点开始的所有路由都需要身份验证，并自动加载用户。Keep in mind that these callbacks do not have to act as end-points: loadUser can perform a task, then call next() to continue matching subsequent routes.请记住，这些回调不必充当端点：loadUser可以执行任务，然后调用next()继续匹配后续路由。

app.all('{*splat}', requireAuthentication, loadUser)

Or the equivalent:或等效物：

app.all('{*splat}', requireAuthentication)
app.all('{*splat}', loadUser)

Another example is white-listed “global” functionality.另一个例子是白名单“全局”功能。 The example is similar to the ones above, but it only restricts paths that start with “/api”:这个例子类似于上面的例子，但它只限制以“/api”开头的路径：

app.all('/api/{*splat}', requireAuthentication)

app.delete(path, callback [, callback ...])

Routes HTTP DELETE requests to the specified path with the specified callback functions.使用指定的回调函数将HTTP DELETE请求路由到指定的路径。 For more information, see the routing guide.有关更多信息，请参阅路线指南。

Arguments参数

Example示例

app.delete('/', (req, res) => {
  res.send('DELETE request to homepage')
})

app.disable(name)

Sets the Boolean setting name to false, where name is one of the properties from the app settings table.将布尔设置name设置为false，其中name是应用程序设置表中的属性之一。 Calling app.set('foo', false) for a Boolean property is the same as calling app.disable('foo').对布尔属性调用app.set('foo', false)与调用app.disable('foo')相同。

For example:例如：

app.disable('trust proxy')
app.get('trust proxy')
// => false

app.disabled(name)

Returns true if the Boolean setting name is disabled (false), where name is one of the properties from the app settings table.如果布尔设置name被禁用（false），则返回true，其中name是应用程序设置表中的属性之一。

app.disabled('trust proxy')
// => true

app.enable('trust proxy')
app.disabled('trust proxy')
// => false

app.enable(name)

Sets the Boolean setting name to true, where name is one of the properties from the app settings table.将布尔设置name设置为true，其中name是应用程序设置表中的属性之一。 Calling app.set('foo', true) for a Boolean property is the same as calling app.enable('foo').为布尔属性调用app.set('foo', true)与调用app.enable('foo')相同。

app.enable('trust proxy')
app.get('trust proxy')
// => true

app.enabled(name)

Returns true if the setting name is enabled (true), where name is one of the properties from the app settings table.如果启用了设置name（true），则返回true，其中name是应用程序设置表中的属性之一。

app.enabled('trust proxy')
// => false

app.enable('trust proxy')
app.enabled('trust proxy')
// => true

app.engine(ext, callback)

Registers the given template engine callback as ext.将给定的模板引擎callback注册为ext。

By default, Express will require() the engine based on the file extension.默认情况下，Express将根据文件扩展名require()引擎。 For example, if you try to render a “foo.pug” file, Express invokes the following internally, and caches the require() on subsequent calls to increase performance.例如，如果您尝试渲染“foo.pug”文件，Express会在内部调用以下内容，并在后续调用中缓存require()以提高性能。

app.engine('pug', require('pug').__express)

Use this method for engines that do not provide .__express out of the box, or if you wish to “map” a different extension to the template engine.对于不提供开箱即用的.__express的发动机，或者如果你想将不同的扩展“映射”到模板引擎，请使用此方法。

For example, to map the EJS template engine to “.html” files:例如，要将EJS模板引擎映射到“.html”文件：

app.engine('html', require('ejs').renderFile)

In this case, EJS provides a .renderFile() method with the same signature that Express expects: (path, options, callback), though note that it aliases this method as ejs.__express internally so if you’re using “.ejs” extensions you don’t need to do anything.在这种情况下，EJS提供了一个.renderFile()方法，该方法具有Express所期望的相同签名：(path, options, callback)，但请注意，它将此方法内部别名为ejs.__express，所以如果你使用的是“ejs”扩展，你什么都不需要做。

Some template engines do not follow this convention. 一些模板引擎不遵循此约定。The consolidate.js library maps Node template engines to follow this convention, so they work seamlessly with Express.consolidate.js库将Node模板引擎映射为遵循此约定，因此它们与Express无缝协作。

const engines = require('consolidate')
app.engine('haml', engines.haml)
app.engine('html', engines.hogan)

app.get(name)

Returns the value of name app setting, where name is one of the strings in the app settings table. For example:返回name app设置的值，其中name是应用程序设置表中的字符串之一。例如：

app.get('title')
// => undefined

app.set('title', 'My Site')
app.get('title')
// => "My Site"

app.get(path, callback [, callback ...])

Routes HTTP GET requests to the specified path with the specified callback functions.使用指定的回调函数将HTTP GET请求路由到指定的路径。

Arguments参数

For more information, see the routing guide.有关更多信息，请参阅路线指南。

Example示例

app.get('/', (req, res) => {
  res.send('GET request to homepage')
})

app.listen(path, [callback])

Starts a UNIX socket and listens for connections on the given path.启动UNIX套接字并侦听给定路径上的连接。 This method is identical to Node’s http.Server.listen().此方法与Node的http.Server.listen()完全相同。

const express = require('express')
const app = express()
app.listen('/tmp/sock')

app.listen([port[, host[, backlog]]][, callback])

Binds and listens for connections on the specified host and port.绑定并侦听指定主机和端口上的连接。 This method is identical to Node’s http.Server.listen().此方法与Node的http.Server.listen()完全相同。

If port is omitted or is 0, the operating system will assign an arbitrary unused port, which is useful for cases like automated tasks (tests, etc.).如果端口被省略或为0，操作系统将分配一个任意未使用的端口，这对于自动化任务（测试等）等情况很有用。

const express = require('express')
const app = express()
app.listen(3000)

The app returned by express() is in fact a JavaScript Function, designed to be passed to Node’s HTTP servers as a callback to handle requests. express()返回的app实际上是一个JavaScript函数，旨在作为回调传递给Node的HTTP服务器以处理请求。This makes it easy to provide both HTTP and HTTPS versions of your app with the same code base, as the app does not inherit from these (it is simply a callback):这使得为应用程序的HTTP和HTTPS版本提供相同的代码库变得容易，因为应用程序不会继承这些代码（它只是一个回调）：

const express = require('express')
const https = require('https')
const http = require('http')
const app = express()

http.createServer(app).listen(80)
https.createServer(options, app).listen(443)

The app.listen() method returns an http.Server object and (for HTTP) is a convenience method for the following:app.listen()方法返回一个http.Server对象，（对于HTTP）是一个方便的方法，用于以下操作：

app.listen = function () {
  const server = http.createServer(this)
  return server.listen.apply(server, arguments)
}

app.METHOD(path, callback [, callback ...])

Routes an HTTP request, where METHOD is the HTTP method of the request, such as GET, PUT, POST, and so on, in lowercase. 路由HTTP请求，其中METHOD是请求的HTTP方法，如GET、PUT、POST等，小写。Thus, the actual methods are app.get(), app.post(), app.put(), and so on. See Routing methods below for the complete list.因此，实际的方法是app.get()、app.post()、app.put()等。有关完整列表，请参阅下面的路由方法。

Arguments参数

Routing methods路由方法

Express supports the following routing methods corresponding to the HTTP methods of the same names:Express支持与同名HTTP方法对应的以下路由方法：

The API documentation has explicit entries only for the most popular HTTP methods app.get(), app.post(), app.put(), and app.delete().API文档中只有最流行的HTTP方法app.get()、app.post()、app.put()和app.delete()的显式条目。 However, the other methods listed above work in exactly the same way.然而，上面列出的其他方法的工作方式完全相同。

To route methods that translate to invalid JavaScript variable names, use the bracket notation. For example, app['m-search']('/', function ....要路由转换为无效JavaScript变量名的方法，请使用括号表示法。例如，app['m-search']('/', function ...。

The method, app.all(), is not derived from any HTTP method and loads middleware at the specified path for all HTTP request methods.方法app.all()不是从任何HTTP方法派生出来的，它在所有HTTP请求方法的指定路径上加载中间件。 For more information, see app.all.有关更多信息，请参阅app.all。

For more information on routing, see the routing guide.有关路由的更多信息，请参阅路由指南。

app.param(name, callback)

Add callback triggers to route parameters, where name is the name of the parameter or an array of them, and callback is the callback function. 在路由参数中添加回调触发器，其中name是参数的名称或它们的数组，callback是回调函数。The parameters of the callback function are the request object, the response object, the next middleware, the value of the parameter and the name of the parameter, in that order.回调函数的参数依次是请求对象、响应对象、下一个中间件、参数值和参数名称。

If name is an array, the callback trigger is registered for each parameter declared in it, in the order in which they are declared. 如果name是一个数组，则会按照声明的顺序为其中声明的每个参数注册callback触发器。Furthermore, for each declared parameter except the last one, a call to next inside the callback will call the callback for the next declared parameter. 此外，对于除最后一个之外的每个声明参数，在回调函数中调用next将调用下一个声明参数的回调函数。For the last parameter, a call to next will call the next middleware in place for the route currently being processed, just like it would if name were just a string.对于最后一个参数，调用next将调用当前正在处理的路由的下一个中间件，就像name只是一个字符串一样。

For example, when :user is present in a route path, you may map user loading logic to automatically provide req.user to the route, or perform validations on the parameter input.例如，当:user出现在路由路径中时，您可以映射用户加载逻辑以自动向路由提供req.user，或对参数输入进行验证。

app.param('user', (req, res, next, id) => {
  // try to get the user details from the User model and attach it to the request object
  User.find(id, (err, user) => {
    if (err) {
      next(err)
    } else if (user) {
      req.user = user
      next()
    } else {
      next(new Error('failed to load user'))
    }
  })
})

Param callback functions are local to the router on which they are defined. They are not inherited by mounted apps or routers, nor are they triggered for route parameters inherited from parent routers. 参数回调函数是定义它们的路由器的本地函数。它们不会被挂载的应用程序或路由器继承，也不会因从父路由器继承的路由参数而触发。Hence, param callbacks defined on app will be triggered only by route parameters defined on app routes.因此，在app上定义的参数回调将仅由在app路由上定义的路由参数触发。

All param callbacks will be called before any handler of any route in which the param occurs, and they will each be called only once in a request-response cycle, even if the parameter is matched in multiple routes, as shown in the following examples.所有参数回调都将在参数出现的任何路由的任何处理程序之前调用，并且它们在请求-响应周期中只会被调用一次，即使参数在多个路由中匹配，如以下示例所示。

app.param('id', (req, res, next, id) => {
  console.log('CALLED ONLY ONCE')
  next()
})

app.get('/user/:id', (req, res, next) => {
  console.log('although this matches')
  next()
})

app.get('/user/:id', (req, res) => {
  console.log('and this matches too')
  res.end()
})

On GET /user/42, the following is printed:在GET /user/42上打印以下内容：

CALLED ONLY ONCE
although this matches
and this matches too

app.param(['id', 'page'], (req, res, next, value) => {
  console.log('CALLED ONLY ONCE with', value)
  next()
})

app.get('/user/:id/:page', (req, res, next) => {
  console.log('although this matches')
  next()
})

app.get('/user/:id/:page', (req, res) => {
  console.log('and this matches too')
  res.end()
})

On GET /user/42/3, the following is printed:在GET /user/42/3上打印以下内容：

CALLED ONLY ONCE with 42
CALLED ONLY ONCE with 3
although this matches
and this matches too

app.path()

Returns the canonical path of the app, a string.返回应用程序的规范路径，一个字符串。

const app = express()
const blog = express()
const blogAdmin = express()

app.use('/blog', blog)
blog.use('/admin', blogAdmin)

console.log(app.path()) // ''
console.log(blog.path()) // '/blog'
console.log(blogAdmin.path()) // '/blog/admin'

The behavior of this method can become very complicated in complex cases of mounted apps: it is usually better to use req.baseUrl to get the canonical path of the app.在安装应用程序的复杂情况下，此方法的行为可能会变得非常复杂：通常最好使用req.baseUrl来获取应用程序的规范路径。

app.post(path, callback [, callback ...])

Routes HTTP POST requests to the specified path with the specified callback functions.使用指定的回调函数将HTTP POST请求路由到指定的路径。 For more information, see the routing guide.有关更多信息，请参阅路线指南。

Arguments参数

Example示例

app.post('/', (req, res) => {
  res.send('POST request to homepage')
})

app.put(path, callback [, callback ...])

Routes HTTP PUT requests to the specified path with the specified callback functions.使用指定的回调函数将HTTP PUT请求路由到指定的路径。

Arguments参数

Example示例

app.put('/', (req, res) => {
  res.send('PUT request to homepage')
})

app.render(view, [locals], callback)

Returns the rendered HTML of a view via the callback function. 通过callback函数返回视图的渲染HTML。It accepts an optional parameter that is an object containing local variables for the view. 它接受一个可选参数，该参数是一个包含视图局部变量的对象。It is like res.render(), except it cannot send the rendered view to the client on its own.它类似于res.render()，只是它不能自己将渲染的视图发送到客户端。

app.render('email', (err, html) => {
  // ...
})

app.render('email', { name: 'Tobi' }, (err, html) => {
  // ...
})

app.route(path)

Returns an instance of a single route, which you can then use to handle HTTP verbs with optional middleware.返回单个路由的实例，然后您可以使用该实例通过可选中间件处理HTTP谓词。 Use app.route() to avoid duplicate route names (and thus typo errors).使用app.route()避免重复的路由名称（从而避免拼写错误）。

const app = express()

app.route('/events')
  .all((req, res, next) => {
    // runs for all HTTP verbs first
    // think of it as route specific middleware!
  })
  .get((req, res, next) => {
    res.json({})
  })
  .post((req, res, next) => {
    // maybe add a new event...
  })

app.set(name, value)

Assigns setting name to value. You may store any value that you want, but certain names can be used to configure the behavior of the server. 将设置name分配给value。您可以存储任何想要的值，但某些名称可用于配置服务器的行为。These special names are listed in the app settings table.这些特殊名称列在应用程序设置表中。

Calling app.set('foo', true) for a Boolean property is the same as calling app.enable('foo'). 为布尔属性调用app.set('foo', true)与调用app.enable('foo')相同。Similarly, calling app.set('foo', false) for a Boolean property is the same as calling app.disable('foo').同样地，对Boolean属性调用app.set('foo', false)与调用app.disable('foo')相同。

Retrieve the value of a setting with app.get().使用app.get()检索设置的值。

app.set('title', 'My Site')
app.get('title') // "My Site"

Application Settings设置

The following table lists application settings.下表列出了应用程序设置。

Note that sub-apps will:请注意，子应用程序将：

• Not inherit the value of settings that have a default value. You must set the value in the sub-app.不继承具有默认值的设置值。您必须在子应用程序中设置该值。
• Inherit the value of settings with no default value; these are explicitly noted in the table below.继承没有默认值的设置值；这些在下表中明确指出。

Exceptions: Sub-apps will inherit the value of trust proxy even though it has a default value (for backward-compatibility);例外情况：子应用程序将继承trust proxy的值，即使它有默认值（为了向后兼容性）； Sub-apps will not inherit the value of view cache in production (when NODE_ENV is “production”).子应用程序在生产环境中不会继承view cache的值（当NODE_ENV为“production”时）。

Options for `trust proxy` settingtrust proxy设置选项

Read Express behind proxies for more information.阅读代理背后的Express以获取更多信息。

app.set('trust proxy', 'loopback')

app.set('trust proxy', 'loopback, 123.123.123.123')

app.set('trust proxy', 'loopback, linklocal, uniquelocal')

app.set('trust proxy', ['loopback', 'linklocal', 'uniquelocal'])

app.set('trust proxy', (ip) => {
  if (ip === '127.0.0.1' || ip === '123.123.123.123') return true // trusted IPs
  else return false
})

Options for `etag` settingetag设置选项

NOTE: These settings apply only to dynamic files, not static files.：这些设置仅适用于动态文件，不适用于静态文件。 The express.static middleware ignores these settings.express.static中间件忽略这些设置。

The ETag functionality is implemented using the etag package.ETag功能是使用etag包实现的。 For more information, see its documentation.有关更多信息，请参阅其文档。

app.set('etag', (body, encoding) => {
  return generateHash(body, encoding) // consider the function is defined
})

app.use([path,] callback [, callback...])

Mounts the specified middleware function or functions at the specified path: the middleware function is executed when the base of the requested path matches path.在指定路径上挂载指定的一个或多个中间件函数：当请求路径的基匹配path时，执行中间件函数。

Arguments参数

Description描述

A route will match any path that follows its path immediately with a “/”.路线将立即用“/”匹配其路径后面的任何路径。 For example: app.use('/apple', ...) will match “/apple”, “/apple/images”, “/apple/images/news”, and so on.例如：app.use('/apple', ...)将匹配“/apple”、“/apple/images”、“/apple/images/news”等。

Since path defaults to “/”, middleware mounted without a path will be executed for every request to the app.由于path默认为“/”，因此对应用程序的每个请求都将执行没有路径的中间件。 For example, this middleware function will be executed for every request to the app:例如，将对应用程序的每个请求执行此中间件函数：

app.use((req, res, next) => {
  console.log('Time: %d', Date.now())
  next()
})

Middleware functions are executed sequentially, therefore the order of middleware inclusion is important.中间件功能是按顺序执行的，因此中间件包含的顺序很重要。

// this middleware will not allow the request to go beyond it
app.use((req, res, next) => {
  res.send('Hello World')
})

// requests will never reach this route
app.get('/', (req, res) => {
  res.send('Welcome')
})

Error-handling middleware错误处理中间件

Error-handling middleware always takes four arguments. You must provide four arguments to identify it as an error-handling middleware function. 错误处理中间件总是需要四个参数。您必须提供四个参数来将其标识为错误处理中间件函数。Even if you don’t need to use the next object, you must specify it to maintain the signature. 即使不需要使用下一个对象，也必须指定它来维护签名。Otherwise, the next object will be interpreted as regular middleware and will fail to handle errors. 否则，next对象将被解释为常规中间件，无法处理错误。For details about error-handling middleware, see: Error handling.有关错误处理中间件的详细信息，请参阅：错误处理。

Define error-handling middleware functions in the same way as other middleware functions, except with four arguments instead of three, specifically with the signature (err, req, res, next)):以与其他中间件函数相同的方式定义错误处理中间件函数，除了使用四个参数而不是三个参数，特别是使用签名(err, req, res, next)：

app.use((err, req, res, next) => {
  console.error(err.stack)
  res.status(500).send('Something broke!')
})

Path examples路径示例

The following table provides some simple examples of valid path values for mounting middleware.下表提供了安装中间件的有效path值的一些简单示例。

app.use('/abcd', (req, res, next) => {
  next()
})

app.use('/ab{c}d', (req, res, next) => {
  next()
})

app.use(/\/abc|\/xyz/, (req, res, next) => {
  next()
})

app.use(['/abcd', '/xyza', /\/lmn|\/pqr/], (req, res, next) => {
  next()
})

Middleware callback function examples中间件回调函数示例

The following table provides some simple examples of middleware functions that can be used as the callback argument to app.use(), app.METHOD(), and app.all().下表提供了一些中间件函数的简单示例，这些函数可以用作app.use()、app.METHOD()和app.all()的callback参数。

app.use((req, res, next) => {
  next()
})

const router = express.Router()
router.get('/', (req, res, next) => {
  next()
})
app.use(router)

const subApp = express()
subApp.get('/', (req, res, next) => {
  next()
})
app.use(subApp)

const r1 = express.Router()
r1.get('/', (req, res, next) => {
  next()
})

const r2 = express.Router()
r2.get('/', (req, res, next) => {
  next()
})

app.use(r1, r2)

const r1 = express.Router()
r1.get('/', (req, res, next) => {
  next()
})

const r2 = express.Router()
r2.get('/', (req, res, next) => {
  next()
})

app.use([r1, r2])

function mw1 (req, res, next) { next() }
function mw2 (req, res, next) { next() }

const r1 = express.Router()
r1.get('/', (req, res, next) => { next() })

const r2 = express.Router()
r2.get('/', (req, res, next) => { next() })

const subApp = express()
subApp.get('/', (req, res, next) => { next() })

app.use(mw1, [mw2, r1, r2], subApp)

Following are some examples of using the express.static middleware in an Express app.以下是在Express应用程序中使用express.static中间件的一些示例。

Serve static content for the app from the “public” directory in the application directory:从应用程序目录中的“public”目录为应用程序提供静态内容：

// GET /style.css etc
app.use(express.static(path.join(__dirname, 'public')))

Mount the middleware at “/static” to serve static content only when their request path is prefixed with “/static”:仅当中间件的请求路径前缀为“/static”时，才将中间件挂载到“/static”以提供静态内容：

// GET /static/style.css etc.
app.use('/static', express.static(path.join(__dirname, 'public')))

Disable logging for static content requests by loading the logger middleware after the static middleware:通过在静态中间件之后加载记录器中间件来禁用静态内容请求的日志记录：

app.use(express.static(path.join(__dirname, 'public')))
app.use(logger())

Serve static files from multiple directories, but give precedence to “./public” over the others:从多个目录提供静态文件，但优先使用“./public”：

app.use(express.static(path.join(__dirname, 'public')))
app.use(express.static(path.join(__dirname, 'files')))
app.use(express.static(path.join(__dirname, 'uploads')))

req.app

This property holds a reference to the instance of the Express application that is using the middleware.此属性包含对使用中间件的Express应用程序实例的引用。

If you follow the pattern in which you create a module that just exports a middleware function and require() it in your main file, then the middleware can access the Express instance via req.app如果您遵循以下模式，即创建一个仅导出中间件函数并在主文件中require()它的模块，那么中间件可以通过req.app访问Express实例

For example:例如：

// index.js
app.get('/viewdirectory', require('./mymiddleware.js'))

// mymiddleware.js
module.exports = (req, res) => {
  res.send(`The views directory is ${req.app.get('views')}`)
}

req.baseUrl

The URL path on which a router instance was mounted.装载路由器实例的URL路径。

The req.baseUrl property is similar to the mountpath property of the app object, except app.mountpath returns the matched path pattern(s).req.baseUrl属性类似于app对象的mountpath属性，只是app.mountpath返回匹配的路径模式。

For example:例如：

const greet = express.Router()

greet.get('/jp', (req, res) => {
  console.log(req.baseUrl) // /greet
  res.send('Konichiwa!')
})

app.use('/greet', greet) // load the router on '/greet'

Even if you use a path pattern or a set of path patterns to load the router, the baseUrl property returns the matched string, not the pattern(s). 即使您使用路径模式或一组路径模式来加载路由器，baseUrl属性也会返回匹配的字符串，而不是模式。In the following example, the greet router is loaded on two path patterns.在以下示例中，greet路由器加载在两种路径模式上。

app.use(['/gre:"param"t', '/hel{l}o'], greet) // load the router on '/gre:"param"t' and '/hel{l}o'

When a request is made to /greet/jp, req.baseUrl is “/greet”. When a request is made to /hello/jp, req.baseUrl is “/hello”.当向/greet/jp发出请求时，req.baseUrl为“/greet”。当向/hello/jp发出请求时，req.baseUrl为“/hello”。

req.body

Contains key-value pairs of data submitted in the request body.包含在请求正文中提交的数据的键值对。 By default, it is undefined, and is populated when you use body-parsing middleware such as express.json() or express.urlencoded().默认情况下，它是undefined，当您使用正文解析中间件（如express.json()或express.urlencoded()）时，它会被填充。

The following example shows how to use body-parsing middleware to populate req.body.以下示例显示了如何使用body解析中间件来填充req.body。

const express = require('express')

const app = express()

app.use(express.json()) // for parsing application/json
app.use(express.urlencoded({ extended: true })) // for parsing application/x-www-form-urlencoded

app.post('/profile', (req, res, next) => {
  console.log(req.body)
  res.json(req.body)
})

req.cookies

When using cookie-parser middleware, this property is an object that contains cookies sent by the request. If the request contains no cookies, it defaults to {}.使用cookie-parser中间件时，此属性是一个包含请求发送的cookie的对象。如果请求不包含Cookie，则默认为{}。

// Cookie: name=tj
console.dir(req.cookies.name)
// => "tj"

If the cookie has been signed, you have to use req.signedCookies.如果cookie已签名，则必须使用req.signedCookies。

For more information, issues, or concerns, see cookie-parser.有关更多信息、问题或疑虑，请参阅cookie-parser。

req.fresh

When the response is still “fresh” in the client’s cache true is returned, otherwise false is returned to indicate that the client cache is now stale and the full response should be sent.当响应在客户端缓存中仍然“新鲜”时，返回true，否则返回false，表示客户端缓存现在已过时，应发送完整响应。

When a client sends the Cache-Control: no-cache request header to indicate an end-to-end reload request, this module will return false to make handling these requests transparent.当客户端发送Cache-Control: no-cache请求标头以指示端到端的重新加载请求时，此模块将返回false以使处理这些请求透明。

Further details for how cache validation works can be found in the HTTP/1.1 Caching Specification.有关缓存验证如何工作的更多详细信息，请参阅HTTP/1.1缓存规范。

console.dir(req.fresh)
// => true

req.host

Contains the host derived from the Host HTTP header.包含从Host HTTP标头派生的主机。

When the trust proxy setting does not evaluate to false, this property will instead get the value from the X-Forwarded-Host header field. 当trust proxy设置未评估为false时，此属性将从X-Forwarded-Host标头字段获取值。This header can be set by the client or by the proxy.此标头可以由客户端或代理设置。

If there is more than one X-Forwarded-Host header in the request, the value of the first header is used. 如果请求中有多个X-Forwarded-Host标头，则使用第一个标头的值。This includes a single header with comma-separated values, in which the first value is used.这包括一个逗号分隔值的单个标头，其中使用了第一个值。

// Host: "example.com:3000"
console.dir(req.host)
// => 'example.com:3000'

// Host: "[::1]:3000"
console.dir(req.host)
// => '[::1]:3000'

req.hostname

Contains the hostname derived from the Host HTTP header.包含从Host HTTP标头派生的主机名。

When the trust proxy setting does not evaluate to false, this property will instead get the value from the X-Forwarded-Host header field. 当trust proxy设置未评估为false时，此属性将从X-Forwarded-Host标头字段获取值。This header can be set by the client or by the proxy.此标头可以由客户端或代理设置。

If there is more than one X-Forwarded-Host header in the request, the value of the first header is used. This includes a single header with comma-separated values, in which the first value is used.如果请求中有多个X-Forwarded-Host标头，则使用第一个标头的值。这包括一个逗号分隔值的单个标头，其中使用了第一个值。

// Host: "example.com:3000"
console.dir(req.hostname)
// => 'example.com'

req.ip

Contains the remote IP address of the request.包含请求的远程IP地址。

When the trust proxy setting does not evaluate to false, the value of this property is derived from the left-most entry in the X-Forwarded-For header. 当trust proxy设置未计算为false时，此属性的值将从X-Forwarded-For标头中最左侧的条目中导出。This header can be set by the client or by the proxy.此标头可以由客户端或代理设置。

console.dir(req.ip)
// => "127.0.0.1"

req.ips

When the trust proxy setting does not evaluate to false, this property contains an array of IP addresses specified in the X-Forwarded-For request header. 当trust proxy设置未计算为false时，此属性包含X-Forwarded-For请求标头中指定的IP地址数组。Otherwise, it contains an empty array. This header can be set by the client or by the proxy.否则，它包含一个贫血的数组。此标头可以由客户端或代理设置。

For example, if X-Forwarded-For is client, proxy1, proxy2, req.ips would be ["client", "proxy1", "proxy2"], where proxy2 is the furthest downstream.例如，如果X-Forwarded-For是client, proxy1, proxy2，req.ips将是["client", "proxy1", "proxy2"]，其中proxy2是最下游的。

req.method

Contains a string corresponding to the HTTP method of the request: GET, POST, PUT, and so on.包含与请求的HTTP方法相对应的字符串：GET、POST、PUT等。

req.originalUrl

This property is much like req.url; however, it retains the original request URL, allowing you to rewrite req.url freely for internal routing purposes. 这个属性很像req.url；但是，它保留了原始请求URL，允许您出于内部路由目的自由重写req.url。For example, the “mounting” feature of app.use() will rewrite req.url to strip the mount point.例如，app.use()的“挂载”特性将重写req.url以剥离挂载点。

// GET /search?q=something
console.dir(req.originalUrl)
// => "/search?q=something"

req.originalUrl is available both in middleware and router objects, and is a combination of req.baseUrl and req.url. Consider following example:req.originalUrl在中间件和路由器对象中都可用，是req.baseUrl和req.url的组合。考虑以下示例：

// GET 'http://www.example.com/admin/new?sort=desc'
app.use('/admin', (req, res, next) => {
  console.dir(req.originalUrl) // '/admin/new?sort=desc'
  console.dir(req.baseUrl) // '/admin'
  console.dir(req.path) // '/new'
  next()
})

req.params

This property is an object containing properties mapped to the named route “parameters”. 此属性是一个包含映射到命名路由“参数”的属性的对象。For example, if you have the route /user/:name, then the “name” property is available as req.params.name. This object defaults to {}.例如，如果您有route/user/:name，则“name”属性可用作req.params.name。此对象默认为{}。

// GET /user/tj
console.dir(req.params.name)
// => "tj"

When you use a regular expression for the route definition, capture groups are provided in the array using req.params[n], where n is the n^th capture group.当您使用正则表达式进行路由定义时，数组中会使用req.params[n]提供捕获组，其中n是第n个捕获组。

app.use(/^\/file\/(.*)$/, (req, res) => {
  // GET /file/javascripts/jquery.js
  console.dir(req.params[0])
  // => "javascripts/jquery.js"
})

If you need to make changes to a key in req.params, use the app.param handler. Changes are applicable only to parameters already defined in the route path.如果需要更改req.params中的键，请使用app.param处理程序。更改仅适用于路线路径中已定义的参数。

Any changes made to the req.params object in a middleware or route handler will be reset.对中间件或路由处理程序中的req.params对象所做的任何更改都将被重置。

req.path

Contains the path part of the request URL.包含请求URL的路径部分。

// example.com/users?sort=desc
console.dir(req.path)
// => "/users"

req.protocol

Contains the request protocol string: either http or (for TLS requests) https.包含请求协议字符串：http或（对于TLS请求）https。

When the trust proxy setting does not evaluate to false, this property will use the value of the X-Forwarded-Proto header field if present.当trust proxy设置未评估为false时，此属性将使用X-Forwarded-Proto标头字段的值（如果存在）。 This header can be set by the client or by the proxy.此标头可以由客户端或代理设置。

console.dir(req.protocol)
// => "http"

req.query

This property is an object containing a property for each query string parameter in the route.此属性是一个对象，包含路由中每个查询字符串参数的属性。 When query parser is set to disabled, it is an empty object {}, otherwise it is the result of the configured query parser.当查询解析器设置为禁用时，它是一个空对象{}，否则它是配置的查询解析器的结果。

The value of this property can be configured with the query parser application setting to work how your application needs it. 此属性的值可以使用查询解析器应用程序设置进行配置，以满足应用程序的需求。A very popular query string parser is the qs module, and this is used by default. 一个非常流行的查询字符串解析器是qs模块，默认情况下使用它。The qs module is very configurable with many settings, and it may be desirable to use different settings than the default to populate req.query:qs模块可以通过许多设置进行配置，可能需要使用与默认设置不同的设置来填充req.query：

const qs = require('qs')
app.set('query parser',
  (str) => qs.parse(str, { /* custom options */ }))

Check out the query parser application setting documentation for other customization options.查看查询解析器应用程序设置文档，了解其他自定义选项。

req.res

This property holds a reference to the response object that relates to this request object.此属性包含对与此请求对象相关的响应对象的引用。

req.route

Contains the currently-matched route, a string. For example:包含当前匹配的路由，一个字符串。例如：

app.get('/user/{:id}', (req, res) => {
  console.dir(req.route, { depth: null })
  res.send('GET')
})

Example output from the previous snippet:上一段代码的示例输出：

Route {
  path: '/user/{:id}',
  stack: [
    Layer {
      handle: [Function (anonymous)],
      keys: [],
      name: '<anonymous>',
      params: undefined,
      path: undefined,
      slash: false,
      matchers: [ [Function: match] ],
      method: 'get'
    }
  ],
  methods: [Object: null prototype] { get: true }
}

req.secure

A Boolean property that is true if a TLS connection is established. Equivalent to the following:一个布尔属性，如果建立了TLS连接，则为true。相当于以下内容：

req.protocol === 'https'

req.signedCookies

When using cookie-parser middleware, this property contains signed cookies sent by the request, unsigned and ready for use. 使用cookie-parser中间件时，此属性包含由请求发送的已签名cookie、未签名cookie和可供使用的cookie。Signed cookies reside in a different object to show developer intent; otherwise, a malicious attack could be placed on req.cookie values (which are easy to spoof). 签名的Cookie驻留在不同的对象中，以显示开发人员的意图；否则，req.cookie值（很容易被欺骗）可能会受到恶意攻击。Note that signing a cookie does not make it “hidden” or encrypted; but simply prevents tampering (because the secret used to sign is private).请注意，对cookie进行签名并不会使其“隐藏”或加密；但只是防止篡改（因为用于签名的秘密是私有的）。

If no signed cookies are sent, the property defaults to {}.如果没有发送签名的Cookie，则属性默认为{}。

// Cookie: user=tobi.CP7AWaXDfAKIRfH49dQzKJx7sKzzSoPq7/AcBBRVwlI3
console.dir(req.signedCookies.user)
// => "tobi"

For more information, issues, or concerns, see cookie-parser.有关更多信息、问题或疑虑，请参阅cookie解析器。

req.stale

Indicates whether the request is “stale,” and is the opposite of req.fresh. For more information, see req.fresh.指示请求是否“过时”，是否与req.fresh相反。有关更多信息，请参阅req.fresh。

console.dir(req.stale)
// => true

req.subdomains

An array of subdomains in the domain name of the request.请求域名中的子域数组。

// Host: "tobi.ferrets.example.com"
console.dir(req.subdomains)
// => ["ferrets", "tobi"]

The application property subdomain offset, which defaults to 2, is used for determining the beginning of the subdomain segments. 应用程序属性subdomain offset默认为2，用于确定子域段的起始位置。To change this behavior, change its value using app.set.要更改此行为，请使用app.set更改其值。

req.xhr

A Boolean property that is true if the request’s X-Requested-With header field is “XMLHttpRequest”, indicating that the request was issued by a client library such as jQuery.如果请求的X-Requested-With头字段为“XMLHttpRequest”，则布尔属性为true，表示该请求是由jQuery等客户端库发出的。

console.dir(req.xhr)
// => true

req.accepts(types)

Checks if the specified content types are acceptable, based on the request’s Accept HTTP header field.根据请求的Accept HTTP标头字段检查指定的内容类型是否可接受。 The method returns the best match, or if none of the specified content types is acceptable, returns false (in which case, the application should respond with 406 "Not Acceptable").该方法返回最佳匹配，或者如果指定的内容类型都不可接受，则返回false（在这种情况下，应用程序应返回406 "Not Acceptable"）。

The type value may be a single MIME type string (such as “application/json”), an extension name such as “json”, a comma-delimited list, or an array. type值可以是单个MIME类型字符串（如“application/json”）、扩展名（如“json”）、逗号分隔的列表或数组。For a list or array, the method returns the best match (if any).对于list或array，该方法返回最佳匹配（如果有的话）。

// Accept: text/html
req.accepts('html')
// => "html"

// Accept: text/*, application/json
req.accepts('html')
// => "html"
req.accepts('text/html')
// => "text/html"
req.accepts(['json', 'text'])
// => "json"
req.accepts('application/json')
// => "application/json"

// Accept: text/*, application/json
req.accepts('image/png')
req.accepts('png')
// => false

// Accept: text/*;q=.5, application/json
req.accepts(['html', 'json'])
// => "json"

For more information, or if you have issues or concerns, see accepts.有关更多信息，或者如果您有问题或疑虑，请参阅accepts。

req.acceptsCharsets(charset [, ...])

Returns the first accepted charset of the specified character sets, based on the request’s Accept-Charset HTTP header field.根据请求的Accept-Charset HTTP标头字段，返回指定字符集的第一个被接受的字符集。 If none of the specified charsets is accepted, returns false.如果指定的字符集都不被接受，则返回false。

For more information, or if you have issues or concerns, see accepts.有关更多信息，或者如果您有问题或疑虑，请参阅accepts。

req.acceptsEncodings(encoding [, ...])

Returns the first accepted encoding of the specified encodings, based on the request’s Accept-Encoding HTTP header field.根据请求的Accept-Encoding HTTP标头字段，返回指定编码的第一个被接受的编码。 If none of the specified encodings is accepted, returns false.如果指定的编码都不被接受，则返回false。

For more information, or if you have issues or concerns, see accepts.有关更多信息，或者如果您有问题或疑虑，请参阅accepts。

req.acceptsLanguages([lang, ...])

Returns the first accepted language of the specified languages, based on the request’s Accept-Language HTTP header field.根据请求的Accept-Language HTTP标头字段，返回指定语言中第一个被接受的语言。 If none of the specified languages is accepted, returns false.如果指定的语言都不被接受，则返回false。

If no lang argument is given, then req.acceptsLanguages() returns all languages from the HTTP Accept-Language header as an Array.如果没有给出lang参数，则req.acceptsLanguages()将从HTTP Accept-Language头部返回所有语言作为数组。

For more information, or if you have issues or concerns, see accepts.有关更多信息，或者如果您有问题或疑虑，请参阅accepts。

Express (5.x) source: Express（5x）来源：request.js line 172

Accepts (2.0) source: Accepts（2.0）来源：index.js line 195

req.get(field)

Returns the specified HTTP request header field (case-insensitive match).返回指定的HTTP请求标头字段（不区分大小写的匹配）。 The Referrer and Referer fields are interchangeable.Referrer和Referer字段可以互换。

req.get('Content-Type')
// => "text/plain"

req.get('content-type')
// => "text/plain"

req.get('Something')
// => undefined

Aliased as req.header(field).别名为req.header(field)。

req.is(type)

Returns the matching content type if the incoming request’s “Content-Type” HTTP header field matches the MIME type specified by the type parameter. 如果传入请求的“content-type”HTTP标头字段与type参数指定的MIME类型匹配，则返回匹配的内容类型。If the request has no body, returns null.如果请求没有正文，则返回null。 Returns false otherwise.否则返回false。

// With Content-Type: text/html; charset=utf-8
req.is('html') // => 'html'
req.is('text/html') // => 'text/html'
req.is('text/*') // => 'text/*'

// When Content-Type is application/json
req.is('json') // => 'json'
req.is('application/json') // => 'application/json'
req.is('application/*') // => 'application/*'

// Using arrays
// When Content-Type is application/json
req.is(['json', 'html']) // => 'json'

// Using multiple arguments
// When Content-Type is application/json
req.is('json', 'html') // => 'json'

req.is('html') // => false
req.is(['xml', 'yaml']) // => false
req.is('xml', 'yaml') // => false

For more information, or if you have issues or concerns, see type-is.有关更多信息，或者如果您有问题或疑虑，请参阅type-is。

req.range(size[, options])

Range header parser.标头解析器。

The size parameter is the maximum size of the resource.size参数是资源的最大大小。

The options parameter is an object that can have the following properties.options参数是一个可以具有以下属性的对象。

An array of ranges will be returned or negative numbers indicating an error parsing.将返回一个范围数组或负数，表示分析错误。

• -2 signals a malformed header string发出格式错误的标头字符串的信号
• -1 signals an unsatisfiable range表示范围不令人满意

// parse header from request
const range = req.range(1000)

// the type of the range
if (range.type === 'bytes') {
  // the ranges
  range.forEach((r) => {
    // do something with r.start and r.end
  })
}

res.app

This property holds a reference to the instance of the Express application that is using the middleware.此属性包含对使用中间件的Express应用程序实例的引用。

res.app is identical to the req.app property in the request object.res.app与请求对象中的res.app属性相同。

res.headersSent

Boolean property that indicates if the app sent HTTP headers for the response.布尔属性，指示应用程序是否为响应发送了HTTP标头。

app.get('/', (req, res) => {
  console.log(res.headersSent) // false
  res.send('OK')
  console.log(res.headersSent) // true
})

res.locals

Use this property to set variables accessible in templates rendered with res.render.使用此属性可以设置在使用res.render渲染的模板中可访问的变量。 The variables set on res.locals are available within a single request-response cycle, and will not be shared between requests.在res.locals上设置的变量在单个请求-响应周期内可用，不会在请求之间共享。

In order to keep local variables for use in template rendering between requests, use app.locals instead.为了在请求之间保留用于模板呈现的局部变量，请改用app.locals。

This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on to templates rendered within the application.此属性对于向应用程序中呈现的模板公开请求级信息（如请求路径名、经过身份验证的用户、用户设置等）非常有用。

app.use((req, res, next) => {
  // Make `user` and `authenticated` available in templates
  res.locals.user = req.user
  res.locals.authenticated = !req.user.anonymous
  next()
})

res.req

This property holds a reference to the request object that relates to this response object.此属性包含对与此响应对象相关的请求对象的引用。

res.append(field [, value])

Appends the specified value to the HTTP response header field. 将指定value附加到HTTP响应标头field。If the header is not already set, it creates the header with the specified value. The value parameter can be a string or an array.如果标题尚未设置，它将创建具有指定值的标题。value参数可以是字符串或数组。

res.append('Link', ['<http://localhost/>', '<http://localhost:3000/>'])
res.append('Set-Cookie', 'foo=bar; Path=/; HttpOnly')
res.append('Warning', '199 Miscellaneous warning')

res.attachment([filename])

Sets the HTTP response Content-Disposition header field to “attachment”. 将HTTP响应Content-Disposition标头字段设置为“attachment”。If a filename is given, then it sets the Content-Type based on the extension name via res.type(), and sets the Content-Disposition “filename=” parameter.如果给定了filename，则它会通过res.type()根据扩展名设置Content-Type，并设置Content-Disposition“filename=”参数。

res.attachment()
// Content-Disposition: attachment

res.attachment('path/to/logo.png')
// Content-Disposition: attachment; filename="logo.png"
// Content-Type: image/png

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

Sets cookie name to value. The value parameter may be a string or object converted to JSON.将cookiename设置为value。value参数可以是转换为JSON的字符串或对象。

The options parameter is an object that can have the following properties.options参数是一个可以具有以下属性的对象。

For example:例如：

res.cookie('name', 'tobi', { domain: '.example.com', path: '/admin', secure: true })
res.cookie('rememberme', '1', { expires: new Date(Date.now() + 900000), httpOnly: true })

You can set multiple cookies in a single response by calling res.cookie multiple times, for example:您可以通过多次调用res.cookie在一个响应中设置多个Cookie，例如：

res
  .status(201)
  .cookie('access_token', `Bearer ${token}`, {
    expires: new Date(Date.now() + 8 * 3600000) // cookie will be removed after 8 hours
  })
  .cookie('test', 'test')
  .redirect(301, '/admin')

The encode option allows you to choose the function used for cookie value encoding. Does not support asynchronous functions.encode选项允许您选择用于cookie值编码的函数不支持异步函数。

Example use case: You need to set a domain-wide cookie for another site in your organization.示例用例：您需要为组织中的另一个站点设置一个域范围的cookie。 This other site (not under your administrative control) does not use URI-encoded cookie values.此其他网站（不受您的管理控制）不使用URI编码的cookie值。

// Default encoding
res.cookie('some_cross_domain_cookie', 'http://mysubdomain.example.com', { domain: 'example.com' })
// Result: 'some_cross_domain_cookie=http%3A%2F%2Fmysubdomain.example.com; Domain=example.com; Path=/'

// Custom encoding
res.cookie('some_cross_domain_cookie', 'http://mysubdomain.example.com', { domain: 'example.com', encode: String })
// Result: 'some_cross_domain_cookie=http://mysubdomain.example.com; Domain=example.com; Path=/;'

The maxAge option is a convenience option for setting “expires” relative to the current time in milliseconds. The following is equivalent to the second example above.maxAge选项是一个方便的选项，用于设置相对于当前时间（毫秒）的“过期”。以下与上述第二个示例等效。

res.cookie('rememberme', '1', { maxAge: 900000, httpOnly: true })

You can pass an object as the value parameter; it is then serialized as JSON and parsed by bodyParser() middleware.您可以将对象作为value参数传递；然后将其序列化为JSON，并由bodyPaser()中间件解析。

res.cookie('cart', { items: [1, 2, 3] })
res.cookie('cart', { items: [1, 2, 3] }, { maxAge: 900000 })

When using cookie-parser middleware, this method also supports signed cookies. 当使用cookie-parser中间件时，此方法也支持签名的cookie。Simply include the signed option set to true.只需将signed选项设置为true即可。 Then, res.cookie() will use the secret passed to cookieParser(secret) to sign the value.然后，res.cookie()将使用传递给cookieParser(secret)的secret对值进行签名。

res.cookie('name', 'tobi', { signed: true })

Later, you may access this value through the req.signedCookies object.稍后，您可以通过req.signedCookies对象访问此值。

res.clearCookie(name [, options])

Clears the cookie with the specified name by sending a Set-Cookie header that sets its expiration date in the past.通过发送Set-Cookie标头来清除具有指定name的cookie，该标头设置了过去的过期日期。 This instructs the client that the cookie has expired and is no longer valid. 这指示客户端cookie已过期，不再有效。For more information about available options, see res.cookie().有关可用options的更多信息，请参阅res.cookie()。

res.cookie('name', 'tobi', { path: '/admin' })
res.clearCookie('name', { path: '/admin' })

res.download(path [, filename] [, options] [, fn])

Transfers the file at path as an “attachment”. Typically, browsers will prompt the user for download.将path中的文件作为“附件”传输。通常，浏览器会提示用户下载。 By default, the Content-Disposition header “filename=” parameter is derived from the path argument, but can be overridden with the filename parameter.默认情况下，Content-Disposition标头“filename=”参数从path参数派生，但可以用filename参数覆盖。 If path is relative, then it will be based on the current working directory of the process or the root option, if provided.如果path是相对的，那么它将基于进程的当前工作目录或root选项（如果提供）。

The following table provides details on the options parameter.下表提供了options参数的详细信息。