node-mysql how to use result outside of an anonymous function

Question

I have a query like below:

connection.query('SELECT * FROM `Users` WHERE `Id` = ?;', [Id], function (err, row) {
var a = row;
});

//how can I use variable `a` in here?

This is basic javascript, I would highly recommend reading a basic tutorial on javascript and callbacks — jeremy
– jeremy, Commented Mar 26, 2014 at 15:01
You'll need to move the stuff after connection.query() into the callback or, perhaps better, call a function and pass the row variable to it. — user440788
– user440788, Commented Mar 26, 2014 at 15:31
You should understand that even thought in your example callback is defined inline you can pass as well function name, it's not that the results of query are inside query, they are passed to function and it can be defined elsewhere (but in accessible scope) — maurycy
– maurycy, Commented Aug 24, 2016 at 11:44

Joseph Dailey · Accepted Answer · 2014-03-26 15:00:47Z

0

you really won't be able to. at least not easily.

var a;
connection.query('SELECT * FROM `Users` WHERE `Id` = ?;', [Id], function (err, row) {
    a = row;
});
//execute stuff

This will accomplish getting the value out into the next scope but where you would //execute stuff will have already happened before a is set. This is because (I'm assuming) node-mysql is asynchronous.

answered Mar 26, 2014 at 15:00

Joseph Dailey

4,9352 gold badges18 silver badges18 bronze badges

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

3 Comments

barry-johnson Over a year ago

You are correct in your assumption as well as your general answer. The OP might find this Q&A which I answered helpful. It provides two approaches (callbacks and promises) for using mysql asynchronously.

Joseph Dailey Over a year ago

Thank you for a assurance, I didn't delve into using callbacks as OP strictly wanted to use a after the call, but thank you for your link.

barry-johnson Over a year ago

Understand entirely. My suspicion is he most likely is somewhat new to node and might not realize he'll probably need to do what he wants inside the callback (for the reason you identified) or come up with a different approach to deferring execution until having the data he wants available.

Collectives™ on Stack Overflow

node-mysql how to use result outside of an anonymous function

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related