如何將函數調用值存儲到變量node.js

Question

我正在創建一個node.js應用程序，它將查看傳遞給它的URL，然後返回正確的數據庫連接字符串。以下是我的genericServer.js文件。第二個代碼塊是我的Connection.js文件。當一個id在URL中傳遞到genericServer文件時，我將它傳遞給中間件connection.getConnString。

var express = require('express'); 
var connection = require('./connection'); 

var connString = ""; 
var app = express(); 

app.get('/connectionString/:id', connection.getConnString, function(res){ 
res.on('response', function(response) { 
    res.on('data', function(chunk) { 
     connString += chunk; 
    console.log("The connection String is: " + connString); 
    }); 
}); 
}); 
app.listen(3333); 

截至目前下面的代碼不會返回正確的連接信息，但我需要關閉在一個變量在（genericserver.js）服務器級別存儲這些數據。我認爲在調用connection.GetConnString中間件之後，我可以使用函數（res）捕獲genericServer.js中的響應。到目前爲止，似乎中間件進程發回了響應，但從未發生函數（res）{}的回調。

有關如何在仍使用app.get（）時將connection.getConnString響應存儲到genericServer調用中的變量的任何想法？

var sql = require('msnodesql'); 
var app = require('express'); 

exports.getConnString = function(req, res) { 

sql.query(conn_str, "SELECT DatabaseLocation, URL FROM dbo.Hospitals WHERE URL = '" + req.params.id + "'", function(err, results) { 
    if (err) { 
     console.log("Error running query!"); 
     console.log(err); return; 
    }; 
    res.writeHead(200, { 
    'Content-Type': 'text/plain' 
}); 

    var connectionString = ""; 
    switch (results[0].DatabaseLocation){ 
     case "172.16.42.243": 
      connectionString = '\"Driver={SQL Server Native Client 11.0};Server=DevelopmentSQL1;Initial Catalog={' + results[0].URL + '};Database={' + results[0].URL + '};UID={userID};PWD={pssWrd};\";' 
      break; 
     case "172.16.42.244": 
      connectionString = '\"Driver={SQL Server Native Client 11.0};Server=DevelopmentSQL2;Initial Catalog={' + results[0].URL + '};Database={' + results[0].URL + '};UID={userID};PWD={pssWrd};\";' 
      break; 
     case "172.16.42.245": 
      connectionString = '\"Driver={SQL Server Native Client 11.0};Server=DevelopmentSQL3;Initial Catalog={' + results[0].URL + '};Database={' + results[0].URL + '};UID={userID};PWD={pssWrd};\";' 
      break; 
     case "172.16.42.246": 
      connectionString = '\"Driver={SQL Server Native Client 11.0};Server=DevelopmentSQL4;Initial Catalog={' + results[0].URL + '};Database={' + results[0].URL + '};UID={userID};PWD={pssWrd};\";' 
      break; 
     case "172.16.42.247": 
      connectionString = '\"Driver={SQL Server Native Client 11.0};Server=DevelopmentSQL5;Initial Catalog={' + results[0].URL + '};Database={' + results[0].URL + '};UID={userID};PWD={pssWrd};\";' 
      break; 
} 
    console.log(connectionString); 
    res.end(connectionString); 
}); 

};

Answer 1

使用響應傳遞數據不是要走的路。在你的中間件，你可以設置連接字符串的req屬性：

exports.getConnString = function(req, res, next) { 
    sql.query(..., function(err, results) { 
    ... // get the connection string as per your code 
    req.connectionString = connectionString; 
    next(); // call the next middleware/route 
    }); 
}; 

你的路由處理會得到下一個叫的，你可以在那裏訪問屬性：

app.get('/connectionString/:id', connection.getConnString, function(req, res) { 
    console.log("The connection String is: ", req.connectionString); 
    res.send(req.connectionString); 
});