How to return value from this function?

Question

This is code in my node.js project but I can't access the value of connection2. I read somewhere that .getConnection is asynchronous function so I can't get the value of connection2 this way. How can I modify this code to properly return the value?

var mysql = require('mysql');
    var connectionPool = mysql.createPool({
        host: 'localhost',
        user: 'root',
        password: '',
        database: 'rockcity_followme'
    });
exports.connExport=function() {
    var connection2;
    connectionPool.getConnection(function (err, connection) {
        connection2=connection;
    });
    return connection2;
}

score 0 · Accepted Answer · edited May 23 '17 at 12:30

0

You cannot return the connection here. It must be asynchronous, so you take a callback as a parameter and call the callback when you have the connection.

exports.connExport=function(callback) {
    connectionPool.getConnection(function (err, connection) {
        callback(connection);
    });
}

See this for more information about asynchronous vs synchronous functions in node.

When a function does anything asynchronously, it has to be asynchronous all the way up. To use connExport from another module, it must be used asynchronously.

var yourModule = require("yourModule");
yourModule.connExport(function(connection) { // <-- the callback function
    // you can use connection here
});

edited May 23 '17 at 12:30

Community

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answered Nov 09 '16 at 09:43

afuous

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This is what I don't understand. Where should I write/define the callback function? Would you please edit your answer a bit? – user3.14 Nov 09 '16 at 09:48
@VikasKumar Does the example usage I added help? – afuous Nov 09 '16 at 09:52

How to return value from this function?

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