Question

app.js

MyDatabase = require("./mysql");
...
var availableRooms = mydb.checkRoomStatus();
console.log("Rooms " + availableRooms);
//undefined.

mysql.js

MyDatabase.prototype.checkRoomStatus = function() {
this.con.query('SELECT * FROM rooms WHERE status = "open" LIMIT 1',function(err,rows){
  if(err) throw err;

  console.log('Data received from Db:\n');
  console.log(rows); // results are coming here.
  return rows;
});

}

第一个console.log正在为availableRooms变量输出“undefined” 我想我应该使用回调函数来处理这种请求但我不知道如何使用它。当我在互联网上搜索时，我找不到任何人使用mysql的单独文件来获得回调结果。

Answer 1

您需要return callback(rows)返回行，并且需要在callback中捕获它们。我希望它清楚。试试这个，看看它是否有效。

将您的mysql代码更改为

MyDatabase.prototype.checkRoomStatus = function(callback) {
this.con.query('SELECT * FROM rooms WHERE status = "open" LIMIT 1',function(err,rows){
  if(err) throw err;

  console.log('Data received from Db:\n');
  console.log(rows); // results are coming here.
  return callback(rows);
});

现在在app.js

MyDatabase = require("./mysql");
...
mydb.checkRoomStatus(function(res){
    var availableRooms = res;
    console.log("Rooms " + availableRooms);
});

node js - 节点mysql - 结果未定义

1 个答案: