其中功能被執行的順序是異步（JavaScript）的

Question

Javascript Code: 

var express = require("express"); 
var mysql  = require('mysql'); 
var app = express(); 

    var speechwindow,id,intent_id,Intent_response; 

function getResults(output,url_id,intent_num,callback) { 
    // The result for speech window 
      var speech = output; 
      console.log(output); 

    // The result for the plotly embed urls 
      var url = 'https://plot.ly/~me/'+url_id+'/'; 
      console.log(url); 
      var img = 'https://plot.ly/~me/'+url_id+'.png'; 
      console.log(img); 
      var data = 'me:'+url_id; 
      console.log(data); 

    // The result for sample utterances 
      var choose = intent_num; 
      var Intent= ['RepeatIntent','CustomOptionIntent','HelpIntent','FinishIntent','OpenEndedOptionTwoIntent','OpenEndedOptionOneIntent','ChangeSetpointIntent','ChoiceIntent']; 
      if (Intent[choose] === 'RepeatIntent'){ 
       var Intent_response = ['repeat the options','can you repeat the options','tell me the options','state the options']; 
      } 
      else if (Intent[choose] === 'CustomOptionIntent') { 
       var Intent_response = ['set the {setpointType} set point to {setPointValue} degree celsius','set the {setpointType} at {setPointValue} degree celsius','{setpointType} is {setPointValue} degrees']; 
      } 
      else if (Intent[choose] === 'HelpIntent'){ 
       var Intent_response = ['what questions can I ask','what are various options which I can know about from you','help me','what commands can I say']; 
      } 
      else if (Intent[choose] === 'FinishIntent'){ 
       var Intent_response = ['exit','quit','bye','leave']; 
      } 
      else if (Intent[choose]=== 'OpenEndedOptionTwoIntent'){ 
       var Intent_response = ['I want to select my own strategy','I want to choose my own strategy','I want to form my custom strategy','I want to form my own strategy']; 
      } 
      else if (Intent[choose] === 'OpenEndedOptionOneIntent'){ 
       var Intent_response = ['which is the best strategy to go with','suggest me the best strategy','provide me with best solution for power consumption','suggest me most efficient power solution']; 
      } 
      else if(Intent[choose] === 'ChangeSetpointIntent'){ 
       var Intent_response = ['what happens if I change {setpointType} to {setPointValue} percent','what happens if I change {setpointType} to {setPointValue} degrees','what will happen if I change the {setpointType} to {setPointValue} degree celsius','I want to change {setpointType} to {setPointValue} degree celsius']; 
      } 
      else if (Intent[choose] === 'ChoiceIntent'){ 
       var Intent_response = ['select option {optionNumber}','select option number {optionNumber}','choose option {optionNumber}']; 
      } 
      console.log(Intent_response); 
      var results = [speech,url,img,data,Intent_response]; 
} 
function generateResponse(req, res) { 
    var connection = mysql.createConnection({ 
      host  : 'localhost', 
      user  : 'user', 
      password : 'password', 
      database : 'mydatabase' 
     }); 
     connection.connect(function(err){ 
     if(!err) { 
      console.log("Database is connected ... \n\n"); 
     } else { 
      console.log("Error connecting database ... \n\n"); 
     } 
     }); 
     connection.query('SELECT * FROM `RTES` ORDER BY ID DESC LIMIT 1', function(err, rows, fields) { 
      if(!err){ 
      var speechwindow = rows[0].ALEXA; 
      console.log(speechwindow); 
      var id = rows[0].URL_ID; 
      console.log(id); 
      var intent_id = rows[0].INTENT_NUM; 
      console.log(intent_id); 
      } 
      else{ 
       console.log('Error');} 
    }); 
      getResults(speechwindow,id,intent_id,function(results) { 
       connection.end(); 
       res.render('dashboard.ejs', {results: results}); 
      }); 
} 

exports.displayResponse = function(req, res){ 
    generateResponse(req, res); 
}; 

輸出窗口：

undefined 
https://plot.ly/~me/undefined/ 
https://plot.ly/~me/undefined.png 
me:undefined 
undefined 
Database is connected ... 


As per my forecast, the best strategy has a lighting of 60 percent, zone temperature of 26 degree celsius, and chilled water temperature of 9 degree celsius, and it leads to a power consumption of 1.23 mega watts. You have a curtailment of 268.00 killo watts than the baseline consumption. In order to continue, you may say state the options or you may say exit if you want to quit. 
113 
7 

我希望我的數據庫被連接並執行getResults功能之前要執行查詢。在輸出窗口中，getResult函數在generateResponse函數之前執行，因此一切都未定義。我試圖把getResult函數作爲generateResponse函數的回調函數，但是我得到了相同的輸出結果。 我查了幾個問題，但沒有得到明確的答案。我不確定要更改什麼，以便該功能以同步方式運行。我是JavaScript新手，也許我對asynchoronous執行的理解是有限的，因此我無法解決這個錯誤。

Answer 1

您需要將getResults調用放在connection.query()回調中，而不是在它之後。