How to pass a parameter to a variable inside a function?

Question

JavaScript

io.sockets.on('connection', function (socket) {
    socket.on('show', function (data) {
        var tmp = {};
        connection.query('SELECT * FROM `name` WHERE `id` = ? LIMIT 1', data, function(err, result) {
            tmp.names = result[0];
            console.log(tmp.names);
        });
        console.log(tmp);
    });
});

Here is a piece of my code. It is necessary to make a selection from the database, then transfer all the data to the tmp.result variable. After running this code, nothing is added. Values ​​from a DB twitch, in function it is deduced, and outside - it is empty. Tried tmp.names = {} after tmp declaration but same result. And first, an empty tmp object is output to the console, and then the already created tmp.names, although the output of tmp is below the code.
How can I correctly pass tmp.names from this function?

Answer 1

The matter is that you confuse synchronous and asynchronous functions. Asynchronous ones are not executed immediately, because they do not return a result, but call a callback. Here in the callback you need to do something with the received value. Essentially, your code will be executed in this order:
1. var tmp = {};
2. connection.query starts working
3. console.log(tmp);
(After a while)
4. connection.query finishes and calls your unnamed function function(err, result){ ... }
5. tmp.names = result[0];
6. console.log(tmp.names);

Answer 2

Sir, yes, you forgot about the asynchrony of the node .. About the main feature of what you write the application on.
As they used to say: "Either the Way of the Samurai , or the Way of the Housewife "