重新踏入網頁開發 (6) - Express - 2

 Express - Route parameters

    Route parameters 可以用來擷取 URL 上的 value。

• server.js

      import express from 'express'
  
      // 建立 express 這 module
      var app = express()
      const port = 8888
  
      // 回傳 { "userId": xxx, "bookId": xxx }
      app.get('/users/:userId/books/:bookId', function (req, res) {
          res.send(req.params)
      })
  
      // 可以用 "-" 分割，回傳 { "userId": xxx, "authorId": xxx, "bookId": xxx }
      app.get('/users/:userId-:authorId-:bookId', function (req, res) {
          res.send(req.params)
      })
  
      // 可以用 "." 分割，回傳 { "userId": xxx, "authorId": xxx, "bookId": xxx }
      app.get('/users/:userId.:authorId.:bookId', function (req, res) {
          res.send(req.params)
      })
  
      app.get('/users', function (req, res) {
          res.send("/users\n")
      })
  
      var server = app.listen(port, function () {
          var host = server.address().address
          var port = server.address().port
          console.log("Example app listening at http://%s:%s", host, port)
      })

• Testing ( curl筆記 )

      $ curl -X GET http://localhost:8888/users/34/books/8989
      {"userId":"34","bookId":"8989"}
  
      $ curl -X GET http://localhost:8888/users/34-789-456
      {"userId":"34","authorId":"789","bookId":"456"}
  
      $ curl -X GET http://localhost:8888/users/34.123.258
      {"userId":"34","authorId":"123","bookId":"258"}
  
      $ curl -X GET http://localhost:8888/users/
      /users

 Express - Route handler

    Route handler 的 callback function 可以使用複數個，只要呼叫 next() 這個 function，便可執行下一個 callback function。

• server.js

      import express from 'express'
  
      // 建立 express 這 module
      var app = express()
      const port = 8888
  
      // 可以塞複數個 callback, 只要確保你有傳和呼叫 next()
      app.get('/normal', function (req, res, next) {
          console.log('Hello from the first callback function!')
          next()
      }, function (req, res) {
          console.log('Hello from the second callback function!')
          res.send("Hi, this is the second callback function!\n")
          res.end()
      })
  
      // array 版
      function callbackA(req, res, next) {
          console.log('Hello from callbackA function!')
          next()
      }
      function callbackB(req, res, next) {
          console.log('Hello from callbackB function!')
          next()
      }
      function callbackC(req, res) {
          console.log('Hello from callbackC function!')
          res.send("Hi, this is callbackC!\n")
          res.end()
      }
  
      app.get('/array', [callbackA, callbackB, callbackC])
  
  
      var server = app.listen(port, function () {
          var host = server.address().address
          var port = server.address().port
          console.log("Example app listening at http://%s:%s", host, port)
      })

• Testing - client( curl筆記 )

      $ curl -X GET http://localhost:8888/normal
      Hi, this is the second callback function!
      $ curl -X GET http://localhost:8888/array
      Hi, this is callbackC!

• Testing - server( curl筆記 )

      $ node Learning/11.Express\&ES6/Route_handler.js 
      Example app listening at http://:::8888
      Hello from the first callback function!
      Hello from the second callback function!
      Hello from callbackA function!
      Hello from callbackB function!
      Hello from callbackC function!

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參考資料 :

1. Express 官網