Node.js does not wait for the MySQL server sends the answer, and continues to work asynchronously - mysql

Question

Print haphazardly and not wait for MySQL send a reply.
var mysql=require('mysql').createConnection({
host:'localhost',user:'root',password:'',database:'dbname',port:3306
});
mysql.connect(function(error){if(error){throw error;}else{console.log('MYSQL SERVER [OK]');}});
console.log('// INI //');
var sql='SELECT * FROM sys_users';
mysql.query(sql,function(error,rows){
if(!error){
for(i=0;i<rows.length;i++){
if(i<rows.length-1)
console.log(rows[i].username);
else console.log(rows[i].username);
}
}else console.log('Error');
});
console.log('// END //');
mysql.end();
would have to print:
MYSQL SERVER [OK]
// INI //
List item
// END //
but nevertheless printed:
// INI //
// END //
MYSQL SERVER [OK]
List item

Answer 1

That's the nature of Node.js - callbacks and async code processing.
If you want to run come code after the database response will be returned, place that code inside the callback:
mysql.query(sql,function(error,rows){
if (!error){
for(i=0;i<rows.length;i++){
if(i<rows.length-1)
console.log(rows[i].username);
else
console.log(rows[i].username);
}
} else {
console.log('Error');
}
/* Code to run. Move it to first `if`, if you want to run it only, when no error will occur. */
console.log('//END //');
});
mysql.end();