Nodejs asynchronous database function needs synchronous answer

Question

I am new to nodejs and am writing some code that needs to query my MySQL database and return a username from a given user_id. I\'ve been reading that all your functions sho

Answer 1

Pass in a callback function to get_current_username and then call that callback function from inside of connect.query's callback:

function get_current_username(current_user_id, callback) {
    console.log(' | Entered get_current_username');
    sqlq = 'SELECT username FROM users WHERE id = ' + current_user_id;
    connection.query(sqlq, function(err, rows, fields) {
      if (err) throw err;
      var current_username = rows[0].username;
      console.log(' | the current_username =' + current_username);        
      callback(current_username);
    });
}

When you go to use this function then, you'd do something like:

get_current_username(12345, function(username) {
   console.log("I am " + username);
});

You could also check out the use of promises/futures. I have a feeling I won't be able to do an explanation of these justice, so I'll link off to this StackOverflow question about understanding Promises.

This is an architectural decision though - some people would prefer to use callbacks, especially if writing a module intended for re-use by 3rd parties. (And in fact, it's probably best to get your head fully wrapped around callbacks in the learning stages here, before adopting something like Promise.)