javascript - 在if语句中检索用于比较的值时出现问题

我有以下变量：

   var userFound = false;

万一这是真的，我想执行以下if语句：

 if (userFound) {
    //
        res.render('pickup/errorAlreadyDelivered', {});

  }

但是，问题在于它没有考虑上述for循环内变量的值更改。下面是代码的大部分。

var userFound = false;

let sql = `SELECT box_id, cubby_id, comport, deliveredToUser
                   FROM recipients
                   WHERE package_password = ?`;

connection.query(sql, [req.session.sessionUserPackagePassword], function(err, rows, fields) {
  if (!err) {
    for (var i = 0; i < rows.length; i++) {
      // Make the comparaison case insensitive

      if ((rows[i].deliveredToUser).toLowerCase() == `no`) {
        userFound = true;



        var comport = rows[i].comport;
        var command = "open" + rows[i].cubby_id;
        var commandClose = "close" + rows[i].cubby_id;
        var commandStatus = "status" + rows[i].cubby_id;



        console.log(command);
        console.log(comport);


        var options = {
          scriptPath: 'python/scripts',
          args: [command, comport, commandClose, commandStatus] // pass arguments to the script here

        };


        PythonShell.run('controlLock.py', options, function(err, results) {
          if (err) {
            res.render('errorConnection', {});
          }
          console.log('results: %j', results);
        });

      }



    }

    // If the query fails to execute
  } else {
    console.log('Error while performing Query.');
    res.render('errorConnection', {});

  }
});
connection.end();

if (userFound) {
  //
  res.render('pickup/errorAlreadyDelivered', {});

}

任何帮助将不胜感激。

最佳答案

即使if（userFound）行未按此顺序编写，也会在if（userFound）行运行之后运行将userFound设置为true的回调。 connection.query是一个异步函数。尝试将userFound逻辑放入回调中，以便在收到查询结果并将userFound设置为true后运行。

connection.query(sql, [req.session.sessionUserPackagePassword], function(err, rows, fields) {
  if (!err) {
    for (var i = 0; i < rows.length; i++) {
      // Make the comparaison case insensitive

      if ((rows[i].deliveredToUser).toLowerCase() == `no`) {
        userFound = true;

        var comport = rows[i].comport;
        var command = "open" + rows[i].cubby_id;
        var commandClose = "close" + rows[i].cubby_id;
        var commandStatus = "status" + rows[i].cubby_id;

        console.log(command);
        console.log(comport);

        var options = {
          scriptPath: 'python/scripts',
          args: [command, comport, commandClose, commandStatus] // pass arguments to the script here

        };


        PythonShell.run('controlLock.py', options, function(err, results) {
          if (err) {
            res.render('errorConnection', {});
          }
          console.log('results: %j', results);
        });

      }
    }

    // If the query fails to execute
  } else {
    console.log('Error while performing Query.');
    res.render('errorConnection', {});
  }
  connection.end();

  if (userFound) {
    //
    res.render('pickup/errorAlreadyDelivered', {});

  }
});

关于javascript - 在if语句中检索用于比较的值时出现问题，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/43443370/