路由

路由是指应用程序的端点 (URI) 如何响应客户端请求。有关路由的介绍，请参见基本路由。

您使用与 HTTP 方法对应的 Express app 对象的方法定义路由；例如，app.get() 处理 GET 请求，app.post 处理 POST 请求。如需完整列表，请参阅 app.METHOD。您还可以使用 app.all() 处理所有 HTTP 方法，使用 app.use() 指定中间件作为回调函数（详见使用中间件）。

这些路由方法指定了一个回调函数（有时称为 "handler functions"），当应用程序接收到对指定路由（端点）和 HTTP 方法的请求时调用。换句话说，应用程序 "listens" 对于匹配指定路由和方法的请求，当它检测到匹配时，它会调用指定的回调函数。

实际上，路由方法可以有多个回调函数作为参数。对于多个回调函数，重要的是提供 next 作为回调函数的参数，然后在函数体中调用 next() 以将控制权移交给下一个回调。

下面的代码是一个非常基本的路由示例。

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

// respond with "hello world" when a GET request is made to the homepage
app.get('/', (req, res) => {
  res.send('hello world')
})

路由方法

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

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

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

路由路径

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app.get('/', (req, res) => {
  res.send('root')
})

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app.get('/about', (req, res) => {
  res.send('about')
})

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app.get('/random.text', (req, res) => {
  res.send('random.text')
})

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app.get('/ab?cd', (req, res) => {
  res.send('ab?cd')
})

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app.get('/ab+cd', (req, res) => {
  res.send('ab+cd')
})

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app.get('/ab*cd', (req, res) => {
  res.send('ab*cd')
})

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app.get('/ab(cd)?e', (req, res) => {
  res.send('ab(cd)?e')
})

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app.get(/a/, (req, res) => {
  res.send('/a/')
})

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app.get(/.*fly$/, (req, res) => {
  res.send('/.*fly$/')
})

路由参数

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Route path: /users/:userId/books/:bookId
Request URL: http://localhost:3000/users/34/books/8989
req.params: { "userId": "34", "bookId": "8989" }

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app.get('/users/:userId/books/:bookId', (req, res) => {
  res.send(req.params)
})

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Route path: /flights/:from-:to
Request URL: http://localhost:3000/flights/LAX-SFO
req.params: { "from": "LAX", "to": "SFO" }

Route path: /plantae/:genus.:species
Request URL: http://localhost:3000/plantae/Prunus.persica
req.params: { "genus": "Prunus", "species": "persica" }

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Route path: /user/:userId(\d+)
Request URL: http://localhost:3000/user/42
req.params: {"userId": "42"}

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路由处理程序

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app.get('/example/a', (req, res) => {
  res.send('Hello from A!')
})

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app.get('/example/b', (req, res, next) => {
  console.log('the response will be sent by the next function ...')
  next()
}, (req, res) => {
  res.send('Hello from B!')
})

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const cb0 = function (req, res, next) {
  console.log('CB0')
  next()
}

const cb1 = function (req, res, next) {
  console.log('CB1')
  next()
}

const cb2 = function (req, res) {
  res.send('Hello from C!')
}

app.get('/example/c', [cb0, cb1, cb2])

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const cb0 = function (req, res, next) {
  console.log('CB0')
  next()
}

const cb1 = function (req, res, next) {
  console.log('CB1')
  next()
}

app.get('/example/d', [cb0, cb1], (req, res, next) => {
  console.log('the response will be sent by the next function ...')
  next()
}, (req, res) => {
  res.send('Hello from D!')
})

响应方法

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方法	描述
res.download()	提示要下载的文件。
res.end()	结束响应过程。
res.json()	发送 JSON 响应。
res.jsonp()	发送带有 JSONP 支持的 JSON 响应。
res.redirect()	重定向请求。
res.render()	渲染视图模板。
res.send()	发送各种类型的响应。
res.sendFile()	将文件作为八位字节流发送。
res.sendStatus()	设置响应状态码并将其字符串表示形式作为响应正文发送。

app.route()

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app.route('/book')
  .get((req, res) => {
    res.send('Get a random book')
  })
  .post((req, res) => {
    res.send('Add a book')
  })
  .put((req, res) => {
    res.send('Update the book')
  })

express.Router

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

// middleware that is specific to this router
router.use((req, res, next) => {
  console.log('Time: ', Date.now())
  next()
})
// define the home page route
router.get('/', (req, res) => {
  res.send('Birds home page')
})
// define the about route
router.get('/about', (req, res) => {
  res.send('About birds')
})

module.exports = router

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const birds = require('./birds')

// ...

app.use('/birds', birds)

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