How to achieve synchronous execution?

Question

Node.js

Before performing any action, I need to check the client's balance using the getBalance() function.
The bottom line is that getBalance inside executes a mysql query and returns the balance, and as you probably already guessed, getBalance does not have time to complete the execution, as the following block code continues its work with an empty variable that must be filled with the client's balance.
What to do in this case?

Answer 1

Forward the callback to getBalance, where you substitute it in place of the mysql query completion callback

/*Объявляем*/
getBalance(resultCallback) {
    connection.query('%QUERY%', resultCallback);
}

/*Используем*/
getBalance(function(err, rows, fields){
// что-то делаем с полученным результатом
});

like so

Answer 2

Use callbacks.
In short, you pass a function to the getBalance function that should be executed when this very balance is received.