Javascript 如何仅在查询完成后运行代码?
我有以下代码:Javascript 如何仅在查询完成后运行代码?,javascript,mysql,node.js,if-statement,Javascript,Mysql,Node.js,If Statement,我有以下代码: var userFound = false; let sql = `SELECT box_id, cubby_id, comport, deliveredToUser FROM recipients WHERE package_password = ?`; connection.query(sql, [req.session.sessionUserPackagePassword], funct
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;
console.log(userFound);
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',
// pass arguments to the script here
args: [command, comport, commandClose, commandStatus]
};
PythonShell.run('controlLock.py', options, function(err, results) {
if (err) {
res.render('errorConnection', {});
}
console.log('results: %j', results);
});
}
}
console.log(userFound);
// If the query fails to execute
} else {
console.log('Error while performing Query.');
res.render('errorConnection', {});
}
});
connection.end();
if (!userFound) {
//
res.render('pickup/errorAlreadyDelivered', {});
connection.end();
}
我在查询外部和底部放置了一个
console.log
,尽管查询值更改为true
,但它首先打印出false
,并首先显示出来,因为console.log
没有等到查询完成后才能存储值。是的,但我需要if(!userFound)语句是外部的,因为下面有代码,我想运行一个else语句来运行下面的代码,如果不满足该条件,则必须将其放入回调函数中,包括“下面的代码”。或者,创建另一个包含“下面的代码”的函数,并从查询回调中调用它。一旦异步获得结果,就需要继续异步处理。你不能期望它神奇地同步可用。但是,如何获取函数内部的值并用函数外部的值替换它呢。依赖于asunc结果的所有内容都必须异步执行。是的,但我需要if(!userFound)语句位于外部,因为下面有代码,如果不满足该条件,我希望运行else语句来运行下面的代码。您必须将其放入回调函数中,包括“下面的代码”。或者,创建另一个包含“下面的代码”的函数,并从查询回调中调用它。一旦异步获得结果,就需要继续异步处理。你不能期望它神奇地同步可用。但是,如何获取函数内部的值并用函数外部的值替换它呢。所有依赖于asunc结果的操作都必须异步执行。
if (!userFound) {
//
res.render('pickup/errorAlreadyDelivered', {});
connection.end();
}
console.log("connection ended " + userFound);