mysql - 从nodejs mysql连接函数返回数据

Question

我正在这样做:

    var mysql = require('mysql');
    var config = require('./../Config.js');

    var connection = mysql.createConnection({
        host: config.databaseConnection.host ,
        user: config.databaseConnection.user,
        password: config.databaseConnection.password,
        database: config.databaseConnection.database
    });

    var executeQuery = function (querystring) {



connection.connect(function (err) {

    if (err) throw err;
    console.log("connected to database successfully");
    connection.query(querystring,function(err,rows){
    if(err) throw err;
    console.log(rows);
    });

});

    }


    module.exports = connection;

我希望我的函数executeQuery 返回“行”中的数据。我对回调进行了大量搜索，但无法理解事情是如何工作的。请帮我解决这个问题。

Answer 1

您可以将回调函数传递给executeQuery函数。类似下面的内容

var executeQuery = function (querystring, myCallbackFunction) {
  connection.connect(function (err) {
    if (err) throw err;
    console.log("connected to database successfully");
    connection.query(querystring, function (err, rows) {
      if (err) throw err;
      console.log(rows);
      myCallbackFunction(rows);
    });
  });
}

const myCallbackFunction = function(rows) {
  // do stuff here with rows
}

executeQuery(querystring, myCallbackFunction)

您还可以采用基于 promise 的方法

var executeQuery = function (querystring) {
  return new Promise((resolve, reject) => {
    connection.connect(function (err) {
      if (err) throw err;
      console.log("connected to database successfully");
      connection.query(querystring, function (err, rows) {
        if (err) throw err;
        console.log(rows);
        resolve(rown);
      });
    });
  });
}

executeQuery(querystring).then((rown) => {
// do stuff here with rows
});

如果你需要循环使用这个，你可以这样做

const allPromises= [];
for (let i = 0; i < loopLength; i+=1) {
  allPromises.push(executeQuery(querystring));
}
Promise.all(allPromises).then((result) => {
  // code here
}