Add every item of an Array to mysql db - mysql

Question

I'm pretty new to Java Script and tried to write a small programm to add users to a database. My problem is, that my programs doesn't add every user ones. It adds the last user as often as there are users in the list. users has more than 2 Objects and all the Objects have all field filled.
for(i = 0; i<users.length; i++)
{
var user = users[i];
console.log(user.lastonline)
pool.getConnection(function(err, connection) {
if (err) throw err;
var quer = connection.query('INSERT INTO users SET `steamid` = '+ connection.escape(user.steamid)+', `name`='+connection.escape(user.name)+', `lastonline`='+connection.escape(user.lastonline)+' ON DUPLICATE KEY UPDATE `name`='+connection.escape(user.name)+', `lastonline`='+connection.escape(user.lastonline)+'', function(err, result) {
connection.release();
});
console.log(quer.sql);
});
}
I tried to rewrite this in a lot of different way, but most time I get something like this:
TypeError: Cannot read property 'steamid' of undefined
for(i = 0; i<users.length; i++)
{
pool.getConnection(function(err, connection) {
console.log(users[i]["steamid"]);
if (err) throw err;
var quer = connection.query('INSERT INTO users SET `steamid` = '+ connection.escape(users[i]["steamid"])+', `name`='+connection.escape(users[i].name)+', `lastonline`='+connection.escape(users[i].lastonline)+' ON DUPLICATE KEY UPDATE `name`='+connection.escape(users[i].name)+', `lastonline`='+connection.escape(users[i].lastonline)+'', function(err, result) {
connection.release();
});
console.log(quer.sql);
});
}
EDIT:
Rest of the programm
var mysql = require('mysql');
var Promise = require("bluebird");
var pool = mysql.createPool({
connectionLimit : 10,
host : 'localhost',
user : 'zar',
password : 'qxLLPa06iEs2Bzsu',
database : 'zar',
socketPath: '/var/run/mysqld/mysqld.sock'
});
pool.on('connection', function (connection) {
console.log("connection made")
});
//my testing users
var users = [];
times = Date.now();
user1 = {steamid:012345678912345658,name:"user1",lastonline:times};
user2 = {steamid:012345678912345628,name:"user2",lastonline:times};
user3 = {steamid:012345678912345618,name:"user3",lastonline:times};
users.push(user1);
users.push(user2);
users.push(user3);

Answer 1

Edit: Fixed to use only one connection.
Previous version was getting a new connection for every user.
You should use Promises:
pool.getConnection((err, connection) => {
if (err) {
console.log(err);
return;
}
var tasks = users.map((user) => {
return new Promise((resolve, reject) => {
if (err) {
return reject(err);
}
var quer = connection.query('INSERT INTO users SET `steamid` = ' + connection.escape(user.steamid) + ', `name`=' + connection.escape(user.name) + ', `lastonline`=' + connection.escape(user.lastonline) + ' ON DUPLICATE KEY UPDATE `name`=' + connection.escape(users.name) + ', `lastonline`=' + connection.escape(users.lastonline) + '', function (err, result) {
if (err) {
return reject(err);
}
resolve(result);
});
});
});
Promise.all(tasks)
.then((results) => {
// Array of results passed in resolve
connection.release();
})
.catch((err) => {
// All errors you reject are catched here
});
});
This should workd but still, you are executing all queries in parallel, which can be pretty aggressive for the DB.
I suggest you to look into bluebird Promise.each for better results.