My node.js program isn't working the way I expect javascript to

Question

I've been using javascript for years, and gotten pretty good at it since I started a web development job, but working with node on a personal project I am having issues.

I create an object

    ;( function( undefined ) {
    'use strict';

    var scrape = {
        data : {},
        scrapers: [],
        init : function( coins, exchanges, trade_paths ) {
            scrape.start_time = new Date().getMilliseconds();
            // Load events
            var Event = require( 'events' );
            // Add an eventEmitter to process
            process.event = new Event.EventEmitter()

            // Now we can load any modules, now that global process is modified ;)
            //require( './bter.js' );
            exchanges.forEach( function( exchange ) {
                console.log( exchange.name + '.js' );
                require( exchange.name.toLower() + '.js' );
            } );

            // Trigger the preload event
            process.event.emit( 'scraper::init', coins );

            // Response to all modules processes
            process.event.on( 'scraper::add', scrape.add );
        },
        add : function( module ) {
            scrape.data[module.name] = module.data;
        }
    };

    // Get list of exchanges, coins, and trade paths
    var sql_data = {
        sql : {},
        db : {},
        coins : [],
        exchanges : [],
        trade_paths : [],
        init : function() {
            sql_data.sql = require( 'mysql' );
            sql_data.db = sql_data.sql.createConnection( {
                host : '127.0.0.1',
                user : 'root',
                password : ''
            } );

            sql_data.db.connect();

            // Get coin list
            sql_data.db.query('SELECT * FROM `node`.`coins` WHERE active=true', function(err, rows, fields) {
                if( typeof rows !== 'undefined' ) {
                    sql_data.coins = rows;
                }
                // Oddly, if no error, its equal to null.
                if( err !== null ) {
                    console.log( err );
                }
            } );

            // Get exchange list
            sql_data.db.query( 'SELECT * FROM `node`.`exchanges` WHERE active=true', function( err, rows, fields ) {
                if( typeof rows !== 'undefined' ) {
                    sql_data.exchanges = rows;
                }
                if( err !== null ) {
                    console.log( err );
                }
            } );

            // Get trade paths
            sql_data.db.query( 'SELECT * FROM `node`.`trade_paths` WHERE active=true',     function( err, rows, fields ) {
                if( typeof rows !== 'undefined' ) {
                    sql_data.trade_paths = rows;
                }
                if( err !== null ) {
                    console.log( err );
                }
            } );

            // Close connection to the database
            sql_data.db.end();
        }
    };

    sql_data.init();

    // Start scraping
    scrape.init( sql_data.coins, sql_data.exchanges, sql_data.trade_paths );
} () );

object.x is not accessible. Not even within object itself. I don't know what to do or how to fix this.

I'm getting [ 'a', 'b', 'c' ] on the exact same version. Are you doing something else weird? — Jonatan Hedborg
– Jonatan Hedborg, Commented Jan 12, 2014 at 2:35
Please check this ideone.com/SxeBCp It produces [ 'a', 'b', 'c' ] only — thefourtheye
– thefourtheye, Commented Jan 12, 2014 at 2:36
I get ['a','b','c'] on 10.7 on Mac. Maybe change to object.x=... to this.x = ['a','b','c'] on line 4? — prototype
– prototype, Commented Jan 12, 2014 at 2:41

Andrey Sidorov · Accepted Answer · 2014-01-12 03:41:40Z

1

Your scrape.init function is called before you received data from mysql. You need to call it inside sql_data.init callback (which you can safely call in third .query() since mysql queries are executed sequentially per connection).

answered Jan 12, 2014 at 3:41

Andrey Sidorov

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1 Comment

Nocare Over a year ago

I very much appreciate it. I start my work within the third callback function from mysql and all is good. Makes perfect sense now that I understand what was going on.

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