Cannot use global variable in NodeJS MySQL

Question

I cannot access the upcoming_matches array inside the MySQL query callback, how come?

I'm greeted with a 'TypeError: Cannot read property '1' of null' error message on the console.log(upcoming_matches[1]); line which indicates that the variable is being reset for some reason (a guess, I'm not very experienced with Javascript)?

var regex = regex code..

while ((upcoming_matches = regex.exec(body)) != null) {
    HLTVID = upcoming_matches[1].split("-");    

    connection.query('SELECT * FROM `csgo_matches` WHERE HLTVID=' + HLTVID[0], function(err, rows, fields) {
        if (err) throw err;
        console.log(upcoming_matches[1]);
    });
}

Community · Accepted Answer · 2017-05-23 12:05:35Z

4

Because at the moment the callback passed to connection.query is executed, the while loop already finished and upcoming_matches is null (because that's the condition for the while loop to stop).

connection.query is asynchronous.

See Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference

edited May 23, 2017 at 12:05

CommunityBot

11 silver badge

answered Dec 2, 2014 at 0:33

Felix Kling

820k181 gold badges1.1k silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Cannot use global variable in NodeJS MySQL

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related