Assign object to variable in node.js

Question

Could someone explain me why I can't pass the rows Object to the clubs variable?

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : '',
  database : 'test'
});
var competition_feed = 'England';
var season_id = 2014;
var clubs = {};

connection.connect();

connection.query('SELECT * FROM clubs WHERE competition_feed=\''+competition_feed+'\' AND season_id='+season_id+';', function(err, rows, fields) {
    if (err) throw err;
    clubs = rows;
});

console.log(clubs);

connection.end();

It seems I'm missing something about variables and scope. Please help :)

MobA11y · Accepted Answer · 2013-06-27 16:08:56Z

1

You can, the reason this doesn't work is because

connection.query(.....)

Is asynchronous. So clubs isn't set to rows until later in the event loop. Much after you are trying to use it. One way to achieve the behavior you want is as follows:

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : '',
  database : 'test'
});
var competition_feed = 'England';
var season_id = 2014;
var clubs = {};

connection.connect();

connection.query('SELECT * FROM clubs WHERE competition_feed=\''+competition_feed+'\' AND season_id='+season_id+';', function(err, rows, fields) {
    if (err) throw err;
    clubs = rows;
    logClubs();
});

function logClubs() {
    console.log(clubs);
}


connection.end();

answered Jun 27, 2013 at 16:08

MobA11y

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1 Comment

octavian Over a year ago

Thought it had something to do with 'asynchronousity' (if that's a word) but couldn't figure out how to exactly achieve this behaviour. Thanks :)

Alec Gorge · Accepted Answer · 2013-06-27 16:09:14Z

1

clubs = rows is executed asynchronously. If you put a console.log right before clubs = rows, you will see it actually executes afterwards despite coming first in the code.

answered Jun 27, 2013 at 16:09

Alec Gorge

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2 Comments

MobA11y Over a year ago

Beat you to it by 21 seconds :)

Alec Gorge Over a year ago

Congrats! :( for me though

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