4.x API

express.json([options])

This is a built-in middleware function in Express. 这是Express中的内置中间件函数。It parses incoming requests with JSON payloads and is based on body-parser.它使用JSON有效负载解析传入请求，并基于主体解析器。

Returns middleware that only parses JSON and only looks at requests where the Content-Type header matches the type option. 返回仅解析JSON并仅查看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，并支持自动扩展gzip和deflate编码。

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

The following table describes the properties of the optional options object.下表介绍了可选options对象的属性。

express.raw([options])

This is a built-in middleware function in Express. 这是Express中的内置中间件函数。It parses incoming request payloads into a Buffer and is based on body-parser.它将传入的请求有效负载解析到Buffer中，并基于主体解析器。

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，并仅查看Content-Type标头与type选项匹配的请求。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，并支持自动扩展gzip和deflate编码。

A new body Buffer containing the parsed data is populated on the request object after the middleware (i.e. req.body), or an empty object ({}) if there was no body to parse, the Content-Type was not matched, or an error occurred.包含已解析数据的新body Buffer在中间件（即req.body）之后填充到request对象上，如果没有要解析的主体、内容类型不匹配或发生错误，则填充到空对象（{}）。

The following table describes the properties of the optional options object.下表介绍了可选options对象的属性。

express.Router([options])

Creates a new router object.创建一个新的router对象。

var router = express.Router([options])

The optional options parameter specifies the behavior of the router.可选的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中的内置中间件函数。It serves static files and is based on serve-static.它服务于静态文件，并基于服务静态文件。

The root argument specifies the root directory from which to serve static assets. root参数指定为静态资产提供服务的根目录。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root目录相结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，它不会发送404响应，而是调用next()以转到下一个中间件，从而允许堆叠和回退。

The following table describes the properties of the options object. 下表介绍了options对象的属性。See also the example below.另请参见下面的示例。

For more information, see Serving static files in Express. 有关详细信息，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dot文件没有特殊处理。
• “deny” - Deny a request for a dotfile, respond with 403, then call next().拒绝对点文件的请求，用403响应，然后调用next()。
• “ignore” - Act as if the dotfile does not exist, respond with 404, then call next().如果点文件不存在，则使用404响应，然后调用next()。

NOTE: With the default value, it will not ignore files in a directory that begins with a dot.注意：对于默认值，它不会忽略以点开头的目录中的文件。

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. 如果此选项为true，则客户端错误（如错误请求或对不存在的文件的请求）将导致此中间件仅调用next()来调用堆栈中的下一个中间件。When false, these errors (even 404s), will invoke next(err).如果为false，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，以便可以将多个物理目录映射到同一web地址，或用于填充不存在文件的路由。

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. 如果您已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。This middleware will also reply to all methods.该中间件还将响应所有方法。

setHeaders

For this option, specify a function to set custom response headers. 对于此选项，请指定用于设置自定义响应标头的函数。Alterations to the headers must occur synchronously.对标题的更改必须同步进行。

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

fn(res, path, stat)

Arguments:参数：

• res, the response object.res，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示例

Here is an example of using the express.static middleware function with an elaborate options object:下面是一个将express.static中间件函数与精心设计的选项对象一起使用的示例：

var options = {
  dotfiles: 'ignore',
  etag: false,
  extensions: ['htm', 'html'],
  index: false,
  maxAge: '1d',
  redirect: false,
  setHeaders: function (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. 这是Express中的内置中间件函数。It parses incoming request payloads into a string and is based on body-parser.它将传入的请求有效负载解析为字符串，并基于主体解析器。

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，该中间件将所有正文解析为字符串，并仅查看Content-Type标头与type选项匹配的请求。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，并支持自动扩展gzip和deflate编码。

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

The following table describes the properties of the optional options object.下表介绍了可选options对象的属性。

express.urlencoded([options])

This is a built-in middleware function in Express. 这是Express中的内置中间件函数。It parses incoming requests with urlencoded payloads and is based on body-parser.它使用URL编码的有效负载解析传入请求，并基于主体解析器。

Returns middleware that only parses urlencoded bodies and only looks at requests where the Content-Type header matches the type option. 返回中间件，该中间件仅解析URL编码的实体，并仅查看Content-Type标头与type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.该解析器只接受主体的UTF-8编码，并支持gzip的自动膨胀和deflate编码。

A new body object containing the parsed data is populated on the request object after the middleware (i.e. req.body), or an empty object ({}) if there was no body to parse, the Content-Type was not matched, or an error occurred. 在中间件（即req.body）之后的请求对象上填充包含已解析数据的新body对象，如果没有要解析的主体、Content-Type不匹配或发生错误，则填充空对象（{}）。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（扩展为false时）或任何类型（扩展为true时）。

The following table describes the properties of the optional options object.下表介绍了可选options对象的属性。

app.locals

The app.locals object has properties that are local variables within the application.app.locals对象的属性是应用程序中的局部变量。

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

console.dir(app.locals.email)
// => 'me@myapp.com'

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.设置后，app.locals属性的值将在应用程序的整个生命周期内保持不变，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. 这对于为模板以及应用程序级数据提供帮助函数非常有用。Local variables are available in middleware via req.app.locals (see req.app)本地变量可通过req.app.locals在中间件中使用（请参见req.app）

app.locals.title = 'My App'
app.locals.strftime = require('strftime')
app.locals.email = 'me@myapp.com'

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安装了子应用的路径模式。

var express = require('express')

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

admin.get('/', function (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，只是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.如果子应用安装在多个路径模式上，则app.mountpath将返回其安装的模式列表，如下例所示。

var admin = express()

admin.get('/', function (req, res) {
  console.dir(admin.mountpath) // [ '/adm*n', '/manager' ]
  res.send('Admin Homepage')
})

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

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

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

The mount event is fired on a sub-app, when it is mounted on a parent app. 在父应用程序上挂载子应用程序时，会在该子应用程序上激发mount事件。The parent app is passed to the callback function.父应用程序被传递给回调函数。

var admin = express()

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

admin.get('/', function (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例子

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，都会对到/secret的请求执行以下回调：

app.all('/secret', function (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. app.all()方法用于映射特定路径前缀或任意匹配的“全局”逻辑。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. 例如，如果将以下内容放在所有其他路由定义的顶部，则需要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('*', requireAuthentication, loadUser)

Or the equivalent:或同等标准：

app.all('*', requireAuthentication)
app.all('*', loadUser)

Another example is white-listed “global” functionality. 另一个例子是白名单上的“全局”功能。The example is similar to the ones above, but it only restricts paths that start with “/api”:该示例与上面的示例类似，但它仅限制以“/api”开头的路径：

app.all('/api/*', 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请求路由到指定路径。For more information, see the routing guide.有关详细信息，请参阅路由指南。

Arguments参数

Example例子

app.delete('/', function (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. 将布尔设置名称设置为false，其中name是app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').为布尔属性调用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已禁用（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app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.如果设置name已启用（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将基于文件扩展名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，如果尝试呈现“foo.pug”文件，Express会在内部调用以下命令，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.如果引擎不提供现成的._express，或者您希望“映射”到模板引擎的其他扩展，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.在本例中，EJS提供了一个.renderFile()方法，其签名与Express所期望的相同：(path, options, callback)，不过请注意，它内部给此方法取别名为ejs.__express，所以使用“.ejs”扩展时，您无需执行任何操作。

Some template engines do not follow this convention. 某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，因此它们可以与Express无缝协作。

var 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 setting的值，其中name是app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请求路由到指定路径。

Arguments参数

For more information, see the routing guide.有关详细信息，请参阅路由指南。

Example例子

app.get('/', function (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().此方法等同于Node的http.Server.listen()。

var express = require('express')
var 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().此方法等同于Node的http.Server.listen()。

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。

var express = require('express')
var 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):这使得使用相同的代码库为应用程序提供HTTP和HTTPS版本变得很容易，因为应用程序不会继承这些代码（它只是一个回调）：

var express = require('express')
var https = require('https')
var http = require('http')
var 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，并且（对于HTTP）是用于以下操作的方便方法：

app.listen = function () {
  var 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. 因此，实际的方法是app.get()、app.post()、app.put()等等。See Routing methods below for the complete list.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. 要路由转换为无效JavaScript变量名的方法，请使用括号表示法。For example, app['m-search']('/', function ....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.有关布线的详细信息，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. 向路由参数添加回调触发器，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为请求对象、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已声明参数，在回调中调用next将调用下一个已声明参数的回调。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，或者对参数输入执行验证。

app.param('user', function (req, res, next, id) {
  // 尝试从用户模型获取用户详细信息，并将其附加到请求对象
  User.find(id, function (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. Param回调函数是定义它们的路由器的本地函数。They are not inherited by mounted apps or routers. 它们不会被装载的应用程序或路由器继承。Hence, param callbacks defined on app will be triggered only by route parameters defined on app routes.因此，app上定义的参数回调将仅由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param回调都将在发生param的任何路由的任何处理程序之前调用，并且在一个请求-响应周期中，即使参数在多个路由中匹配，它们也只会被调用一次，如以下示例所示。

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

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

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

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

CALLED ONLY ONCE
although this matches
and this matches too

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

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

app.get('/user/:id/:page', function (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，将打印以下内容：

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

The behavior of the app.param(name, callback) method can be altered entirely by passing only a function to app.param(). app.param(name, callback)方法的行为可以通过只向app.param()传递一个函数来完全改变。This function is a custom implementation of how app.param(name, callback) should behave - it accepts two parameters and must return a middleware.此函数是app.param(name, callback)行为方式的自定义实现-它接受两个参数，并且必须返回一个中间件。

The first parameter of this function is the name of the URL parameter that should be captured, the second parameter can be any JavaScript object which might be used for returning the middleware implementation.此函数的第一个参数是应该捕获的URL参数的名称，第二个参数可以是任何JavaScript对象，该对象可能用于返回中间件实现。

The middleware returned by the function decides the behavior of what happens when a URL parameter is captured.函数返回的中间件决定捕获URL参数时发生的行为。

In this example, the app.param(name, callback) signature is modified to app.param(name, accessId). 在本例中，app.param(name, callback)签名修改为app.param(name, accessId)。Instead of accepting a name and a callback, app.param() will now accept a name and a number.app.param()不再接受名称和回调，而是接受名称和数字。

var express = require('express')
var app = express()

// 自定义app.param()的行为
app.param(function (param, option) {
  return function (req, res, next, val) {
    if (val === option) {
      next()
    } else {
      next('route')
    }
  }
})

// using the customized app.param()
app.param('id', 1337)

// route to trigger the capture
app.get('/user/:id', function (req, res) {
  res.send('OK')
})

app.listen(3000, function () {
  console.log('Ready')
})

In this example, the app.param(name, callback) signature remains the same, but instead of a middleware callback, a custom data type checking function has been defined to validate the data type of the user id.在本例中，app.param(name, callback)签名保持不变，但定义了一个自定义数据类型检查函数来验证用户id的数据类型，而不是中间件回调。

app.param(function (param, validator) {
  return function (req, res, next, val) {
    if (validator(val)) {
      next()
    } else {
      next('route')
    }
  }
})

app.param('id', function (candidate) {
  return !isNaN(parseFloat(candidate)) && isFinite(candidate)
})

// captures '1-a_6' but not '543-azser-sder'
router.get('/[0-9]+-[[\\w]]*', function (req, res, next) { next() })

// captures '1-a_6' and '543-az(ser"-sder' but not '5-a s'
router.get('/[0-9]+-[[\\S]]*', function (req, res, next) { next() })

// captures all (equivalent to '.*')
router.get('[[\\s\\S]]*', function (req, res, next) { next() })

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。

var app = express()
var blog = express()
var blogAdmin = express()

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

console.dir(app.path()) // ''
console.dir(blog.path()) // '/blog'
console.dir(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.在装载应用程序的复杂情况下，此方法的行为可能变得非常复杂：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请求路由到指定路径。For more information, see the routing guide.有关详细信息，请参阅路由指南。

Arguments参数

Example例子

app.post('/', function (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请求路由到指定路径。

Arguments参数

Example例子

app.put('/', function (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返回视图的呈现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.它与res.render()类似，只是它不能单独将渲染视图发送到客户端。

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

app.render('email', { name: 'Tobi' }, function (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，然后可以使用该实例使用可选中间件处理HTTP谓词。Use app.route() to avoid duplicate route names (and thus typo errors).使用app.route()可以避免重复的路由名称（从而避免输入错误）。

var app = express()

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

app.set(name, value)

Assigns setting name to value. 将设置name指定给value。You may store any value that you want, but certain names can be used to configure the behavior of the server. 您可以存储所需的任何值，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').类似地，为布尔属性调用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应用程序设置

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的值。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；下表中明确指出了这些问题。

Exceptions: Sub-apps will inherit the value of trust proxy even though it has a default value (for backward-compatibility); Sub-apps will not inherit the value of view cache in production (when NODE_ENV is “production”).例外情况：子应用程序将继承trust proxy的值，即使它有一个默认值（用于向后兼容）；子应用程序将不会在生产中继承view cache的值（当NODE_ENV为“production”时）。

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', function (ip) {
  if (ip === '127.0.0.1' || ip === '123.123.123.123') return true // trusted IPs
  else return false
})

app.set('etag', function (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.将指定的一个或多个中间件函数装入指定路径：当请求路径的基与路径匹配时，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 “/”. 路由将立即用“/”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“/”，因此将对应用程序的每个请求执行未安装路径的中间件。
For example, this middleware function will be executed for every request to the app:例如，此中间件函数将针对应用程序的每个请求执行：

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

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

// 此中间件将不允许请求超出它的范围
app.use(function (req, res, next) {
  res.send('Hello World')
})

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

Error-handling middleware错误处理中间件

Error-handling middleware always takes four arguments. 错误处理中间件始终具有四个参数。You must provide four arguments to identify it as an error-handling middleware function. 必须提供四个参数才能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next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(function (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.下表提供了一些用于安装中间件的有效路径值的简单示例。

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

app.use('/abc?d', function (req, res, next) {
  next()
})

app.use('/ab+cd', function (req, res, next) {
  next()
})

app.use('/ab*cd', function (req, res, next) {
  next()
})

app.use('/a(bc)?d', function (req, res, next) {
  next()
})

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

app.use(['/abcd', '/xyza', /\/lmn|\/pqr/], function (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，这些函数可用作app.use()、app.METHOD()和app.all()的callback参数。Even though the examples are for app.use(), they are also valid for app.use(), app.METHOD(), and app.all().尽管这些示例适用于app.use()，但它们也适用于app.use()、app.METHOD()和app.all()。

app.use(function (req, res, next) {
  next()
})

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

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

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

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

app.use(r1, r2)

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

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

app.use([r1, r2])

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

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

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

var subApp = express()
subApp.get('/', function (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.下面是在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”:在“/static”处装载中间件，仅当其请求路径前缀为“/static”时，才提供静态内容：

// 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，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:提供来自多个目录的静态文件，但优先于“/public”其他目录：

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如果按照创建模块的模式，只导出中间件函数并在主文件中require()它，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 = function (req, res) {
  res.send('The views directory is ' + req.app.get('views'))
}

req.baseUrl

The URL path on which a router instance was mounted.安装路由器实例的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属性与app对象的mountpath属性类似，只是app.mountpath返回匹配的路径模式。

For example:例如：

var greet = express.Router()

greet.get('/jp', function (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). 即使使用路径模式或一组路径模式加载路由器，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.在下面的示例中，greet路由器加载在两个路径模式上。

app.use(['/gre+t', '/hel{2}o'], greet) // load the router on '/gre+t' and '/hel{2}o'

When a request is made to /greet/jp, req.baseUrl is “/greet”. 当向/greet/jp发出请求时，req.baseUrl为“/greet”。When a request is made to /hello/jp, req.baseUrl is “/hello”.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，它是未定义的，并且在使用主体解析中间件（如express.json()或express.urlencoded()时填充。

The following example shows how to use body-parsing middleware to populate req.body.下面的示例显示如何使用主体解析中间件来填充req.body。

var express = require('express')

var 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', function (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解析器中间件时，此属性是包含请求发送的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、问题或关注点，请参阅cookie解析器。

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，以指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.有关缓存验证工作原理的更多详细信息，请参阅HTTP/1.1缓存规范。

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

req.hostname

Contains the hostname derived from the Host HTTP header.包含从HostHTTP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设置的计算结果不为false时，此属性将改为从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.这包括一个带有逗号分隔值的标题，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设置的计算结果不为false时，此属性的值将从X-Forwarded-For标头中最左侧的条目中派生。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设置的计算结果不为false时，此属性包含在X-Forwarded-For请求标头中指定的IP地址数组。Otherwise, it contains an empty array. 否则，它将包含一个空数组。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。

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，则req.ips将是 ["client", "proxy1", "proxy2"]，其中proxy2是最远的下游。

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方法对应的字符串：GET、POST、PUT等等。

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“装载”功能将重写req.url以剥离装载点。

// 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. 在中间件和路由器对象中都可用，并且是req.baseUrl和req.url的组合。Consider following example:考虑下面的例子：

app.use('/admin', function (req, res, next) { // GET 'http://www.example.com/admin/new?sort=desc'
  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”. 此属性是包含映射到命名管线“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. 例如，如果您有route/user/:name，则“name”属性可用作req.params.name。This object defaults to {}.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. 当您对路由定义使用正则表达式时，将在数组中使用req.params[n]提供捕获组，其中n是第n个捕获组。This rule is applied to unnamed wild card matches with string routes such as /file/*:此规则应用于具有字符串路由的未命名通配符匹配，例如/file/*：

// 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. 如果需要更改req.params中的键，请使用app.param处理程序。Changes are applicable only to parameters already defined in the route path.更改仅适用于管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设置的计算结果不为false时，此属性将使用X-Forwarded-Proto标头字段（如果存在）的值。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。

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{}，否则它是已配置查询解析器的结果。

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?', function userIdHandler (req, res) {
  console.log(req.route)
  res.send('GET')
})

Example output from the previous snippet:上一个代码段的输出示例：

{ path: '/user/:id?',
  stack:
   [ { handle: [Function: userIdHandler],
       name: 'userIdHandler',
       params: undefined,
       path: undefined,
       keys: [],
       regexp: /^\/?$/i,
       method: 'get' } ],
  methods: { get: true } }

req.secure

A Boolean property that is true if a TLS connection is established. Equivalent to:如果建立TLS连接，则为true的布尔属性。相当于：

console.dir(req.protocol === 'https')
// => true

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签名cookie、未签名cookie和可供使用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cookie驻留在不同的对象中，以显示开发人员的意图；否则，可能会对req.cookie值（很容易欺骗）进行恶意攻击。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 {}.如果未发送签名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、问题或关注点，请参阅cookie解析器。

req.stale

Indicates whether the request is “stale,” and is the opposite of req.fresh. 指示请求是否“过时”，恰与req.fresh相反。For more information, see req.fresh.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.请求的域名中的子域数组。

// 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（默认值为2）用于确定子域段的开头。To change this behavior, change its value using app.set.若要更改此行为，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.一个布尔属性，如果请求的X-request-With标头字段为“XMLHttpRequest”，则为true，表示该请求是由jQuery之类的客户端库发出的。

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AcceptHTTP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，应用程序应以406 "Not Acceptable"作为响应）。

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).对于列表或数组，该方法返回最佳匹配（如果有）。

// 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顾虑，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. 基于请求的Accept-CharsetHTTP标头字段，返回指定字符集的第一个接受字符集。If none of the specified charsets is accepted, returns false.如果未接受任何指定的字符集，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顾虑，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-EncodingHTTP标头字段，返回指定编码的第一个接受编码。If none of the specified encodings is accepted, returns false.如果未接受任何指定的编码，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顾虑，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-LanguageHTTP标头字段，返回指定语言中的第一个接受语言。If none of the specified languages is accepted, returns false.如果未接受任何指定语言，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顾虑，请参阅accepts。

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-TypeHTTP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/*'

req.is('html')
// => 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顾虑，请参阅type-is。

req.param(name [, defaultValue])

Returns the value of param name when present.返回参数name的值（如果存在）。

// ?name=tobi
req.param('name')
// => "tobi"

// POST name=tobi
req.param('name')
// => "tobi"

// /user/tobi for /user/:name
req.param('name')
// => "tobi"

Lookup is performed in the following order:按以下顺序执行查找：

• req.params
• req.body
• req.query

Optionally, you can specify defaultValue to set a default value if the parameter is not found in any of the request objects.或者，如果在任何请求对象中都找不到该参数，则可以指定defaultValue来设置默认值。

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，表示解析错误。

• -2 signals a malformed header string向格式错误的标题字符串发送信号
• -1 signals an unsatisfiable range表示无法满足的范围

// 从请求解析标头
var range = req.range(1000)

// the type of the range
if (range.type === 'bytes') {
  // the ranges
  range.forEach(function (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req.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HTTP标头。

app.get('/', function (req, res) {
  console.dir(res.headersSent) // false
  res.send('OK')
  console.dir(res.headersSent) // true
})

res.locals

An object that contains response local variables scoped to the request, and therefore available only to the view(s) rendered during that request / response cycle (if any). 包含响应局部变量的对象，作用域为请求，因此仅对在该请求/响应周期（如果有）期间呈现的视图可用。Otherwise, this property is identical to app.locals.否则，此属性与app.locals相同。

This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on.此属性对于公开请求级信息（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(function (req, res, next) {
  res.locals.user = req.user
  res.locals.authenticated = !req.user.anonymous
  next()
})

res.append(field [, value])

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

Note: calling res.set() after res.append() will reset the previously-set header value.注意：在res.append()之后调用res.set()将重置先前设置的头值。

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.如果给定了文件名，则会通过res.Type()根据扩展名设置内容类型，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. 将cookiename设置为value。The value parameter may be a string or object converted to JSON.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:通过多次调用res.cookie，可以在单个响应中设置多个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. encode选项允许您选择用于cookie值编码的函数。Does not support asynchronous functions.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域范围的cookie。This other site (not under your administrative control) does not use URI-encoded cookie values.此其他站点（不在您的管理控制下）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. maxAge选项是一个方便的选项，用于设置相对于当前时间（以毫秒为单位）的“expires”。The following is equivalent to the second example above.以下内容相当于上面的第二个示例。

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.可以将对象作为value参数传递；然后将其序列化为JSON并由bodyParser()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，此方法还支持签名cookie。Simply include the signed option set to true. 只需将signed选项设置为true。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)的密钥以对值进行签名。

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

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

res.clearCookie(name [, options])

Clears the cookie specified by name. 清除由名称指定的cookie。For details about the options object, see res.cookie().有关选项对象的详细信息，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”. 将path处的文件作为“附件”传输。Typically, browsers will prompt the user for download. 通常，浏览器会提示用户下载。By default, the Content-Disposition header “filename=” parameter is path (this typically appears in the browser dialog). 默认情况下，Content-Disposition标头“filename=”参数为path（通常显示在浏览器对话框中）。Override this default with the filename parameter.使用filename参数覆盖此默认值。

When an error occurs or transfer is complete, the method calls the optional callback function fn. 当发生错误或传输完成时，该方法调用可选的回调函数fn。This method uses res.sendFile() to transfer the file.此方法使用res.sendFile()传输文件。

The optional options argument passes through to the underlying res.sendFile() call, and takes the exact same parameters.可选options参数传递给底层的res.sendFile()调用，并采用完全相同的参数。

res.download('/report-12345.pdf')

res.download('/report-12345.pdf', 'report.pdf')

res.download('/report-12345.pdf', 'report.pdf', function (err) {
  if (err) {
    // 处理错误，但请记住响应可能是部分发送的
    // 所以应检查res.headersSent
  } else {
    // decrement a download credit, etc.
  }
})

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

Ends the response process. 结束响应过程。This method actually comes from Node core, specifically the response.end() method of http.ServerResponse.这个方法实际上来自Node核心，特别是http.ServerResponse的response.end()方法。

Use to quickly end the response without any data. 用于在没有任何数据的情况下快速结束响应。If you need to respond with data, instead use methods such as res.send() and res.json().如果需要使用数据进行响应，请改用res.send()和res.json()等方法。

res.end()
res.status(404).end()

res.format(object)

Performs content-negotiation on the Accept HTTP header on the request object, when present. 在请求对象上的AcceptHTTP标头上执行内容协商（如果存在）。It uses req.accepts() to select a handler for the request, based on the acceptable types ordered by their quality values. 它使用req.accepts()根据可接受类型的质量值排序，为请求选择一个处理程序。If the header is not specified, the first callback is invoked. When no match is found, the server responds with 406 “Not Acceptable”, or invokes the default callback.如果未指定标头，则调用第一个回调。当未找到匹配项时，服务器将以406“不可接受”响应，或调用default回调。

The Content-Type response header is set when a callback is selected. 选择回调时，将设置Content-Type响应标头。However, you may alter this within the callback using methods such as res.set() or res.type().但是，您可以使用res.set()或res.type()等方法在回调中更改此设置。

The following example would respond with { "message": "hey" } when the Accept header field is set to “application/json” or “*/json” (however if it is “*/*”, then the response will be “hey”).下面的示例当Accept头字段设置为“application/json”或“*/json”时将用{ "message": "hey" }作为响应（但是如果是“*/*”，则响应将是“hey”）。

res.format({
  'text/plain': function () {
    res.send('hey')
  },

  'text/html': function () {
    res.send('<p>hey</p>')
  },

  'application/json': function () {
    res.send({ message: 'hey' })
  },

  default: function () {
    // log the request and respond with 406
    res.status(406).send('Not Acceptable')
  }
})

In addition to canonicalized MIME types, you may also use extension names mapped to these types for a slightly less verbose implementation:除了规范化的MIME类型外，您还可以使用映射到这些类型的扩展名来实现稍微不那么详细的实现：

res.format({
  text: function () {
    res.send('hey')
  },

  html: function () {
    res.send('<p>hey</p>')
  },

  json: function () {
    res.send({ message: 'hey' })
  }
})

res.get(field)

Returns the HTTP response header specified by field. 返回由field指定的HTTP响应头。The match is case-insensitive.匹配不区分大小写。

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

res.json([body])

Sends a JSON response. 发送JSON响应。This method sends a response (with the correct content-type) that is the parameter converted to a JSON string using JSON.stringify().此方法发送一个响应（具有正确的内容类型），该响应是使用JSON.stringify()转换为JSON字符串的参数。

The parameter can be any JSON type, including object, array, string, Boolean, number, or null, and you can also use it to convert other values to JSON.该参数可以是任何JSON类型，包括object、array、string、Boolean、number或null，您还可以使用它将其他值转换为JSON。

res.json(null)
res.json({ user: 'tobi' })
res.status(500).json({ error: 'message' })

res.jsonp([body])

Sends a JSON response with JSONP support. 发送带有JSONP支持的JSON响应。This method is identical to res.json(), except that it opts-in to JSONP callback support.此方法与res.json()相同，只是它选择了JSONP回调支持。

res.jsonp(null)
// => callback(null)

res.jsonp({ user: 'tobi' })
// => callback({ "user": "tobi" })

res.status(500).jsonp({ error: 'message' })
// => callback({ "error": "message" })

By default, the JSONP callback name is simply callback. 默认情况下，JSONP回调名称只是callback。Override this with the jsonp callback name setting.使用jsonp回调名称设置覆盖此设置。

The following are some examples of JSONP responses using the same code:以下是使用相同代码的JSONP响应的一些示例：

// ?callback=foo
res.jsonp({ user: 'tobi' })
// => foo({ "user": "tobi" })

app.set('jsonp callback name', 'cb')

// ?cb=foo
res.status(500).jsonp({ error: 'message' })
// => foo({ "error": "message" })

res.links(links)

Joins the links provided as properties of the parameter to populate the response’s Link HTTP header field.加入作为参数属性提供的links，以填充响应的HTTP标头Link字段。

For example, the following call:例如，以下调用：

res.links({
  next: 'http://api.example.com/users?page=2',
  last: 'http://api.example.com/users?page=5'
})

Yields the following results:产生以下结果：

Link: <http://api.example.com/users?page=2>; rel="next",
      <http://api.example.com/users?page=5>; rel="last"

res.location(path)

Sets the response Location HTTP header to the specified path parameter.将响应HTTP标头Location设置为指定的path参数。

res.location('/foo/bar')
res.location('http://example.com')
res.location('back')

A path value of “back” has a special meaning, it refers to the URL specified in the Referer header of the request. path值“back”具有特殊含义，它指的是请求的Referer头中指定的URL。If the Referer header was not specified, it refers to “/”.如果未指定Referer标头，则它引用“/”。

res.redirect([status,] path)

Redirects to the URL derived from the specified path, with specified status, a positive integer that corresponds to an HTTP status code . 重定向到从具有指定status的指定path派生的URL，该URL为与HTTP状态代码对应的正整数。If not specified, status defaults to “302 “Found”.如果未指定，则status默认为“302已找到”。

res.redirect('/foo/bar')
res.redirect('http://example.com')
res.redirect(301, 'http://example.com')
res.redirect('../login')

Redirects can be a fully-qualified URL for redirecting to a different site:重定向可以是完全限定的URL，用于重定向到其他站点：

res.redirect('http://google.com')

Redirects can be relative to the root of the host name. 重定向可以相对于主机名的根。For example, if the application is on http://example.com/admin/post/new, the following would redirect to the URL http://example.com/admin:

res.redirect('/admin')

Redirects can be relative to the current URL. For example, from http://example.com/blog/admin/ (notice the trailing slash), the following would redirect to the URL http://example.com/blog/admin/post/new.

res.redirect('post/new')

Redirecting to post/new from http://example.com/blog/admin (no trailing slash), will redirect to http://example.com/blog/post/new.

If you found the above behavior confusing, think of path segments as directories (with trailing slashes) and files, it will start to make sense.如果您发现上述行为令人困惑，请将路径段视为目录（带有尾随斜杠）和文件，这将开始有意义。

Path-relative redirects are also possible. 路径相对重定向也是可能的。If you were on http://example.com/admin/post/new, the following would redirect to http://example.com/admin/post:

res.redirect('..')

A back redirection redirects the request back to the referer, defaulting to / when the referer is missing.back重定向将请求重定向回referer，当referer丢失时默认为/。

res.redirect('back')

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

Renders a view and sends the rendered HTML string to the client. 呈现view并将呈现的HTML字符串发送到客户端。Optional parameters:可选参数：

• locals, an object whose properties define local variables for the view.，一个对象，其属性定义视图的局部变量。
• callback, a callback function. ，一个回调函数。If provided, the method returns both the possible error and rendered string, but does not perform an automated response. 如果提供，该方法将返回可能的错误和呈现的字符串，但不执行自动响应。When an error occurs, the method invokes next(err) internally.当发生错误时，该方法在内部调用next(err)。

The view argument is a string that is the file path of the view file to render. view参数是一个字符串，它是要渲染的视图文件的文件路径。This can be an absolute path, or a path relative to the views setting. 这可以是绝对路径，也可以是相对于views设置的路径。If the path does not contain a file extension, then the view engine setting determines the file extension. 如果路径不包含文件扩展名，则view engine设置将确定文件扩展名。If the path does contain a file extension, then Express will load the module for the specified template engine (via require()) and render it using the loaded module’s __express function.如果路径确实包含文件扩展名，则Express将加载指定模板引擎的模块（通过require()），并使用加载的模块的__express函数进行渲染。