Question

I have a problem with node.js. The commands of the program doesn’t load cronologically and i don’t know how to do it.
I’m trying to download some images and text from database and send it with packs of 8. But node.js runs for loop and command after loop at the same time.

Here’s my code:

socket.on('background_dinamically', function(data){
        connection.query("SELECT * FROM products WHERE id='"+data.cathegory+"'" , function(err, rows, fields){
            var count = 0;
            var array_elements = [];
            if(err){
                socket.emit('errorserver');
            }else{
                for (var i = rows.length - 1, count; i >= 0; i-- & count ++) {
                    array_elements.push(rows[i]);
                    if (count == 8) {
                        socket.emit('image_loading_background', [array_elements, data]);
                        count = 0;
                        array_elements = [];
                    }
                };

                if(count > 0 && count < 8 && count != 0) { 
                    socket.emit('image_loading_background', [array_elements, data]);
                }
            }
        });
    }); 

Answer 1

Marc, first I would check if synchronisation can be done on the client side. If you force your nodejs app to synchronize before sending data to the client, scalability suffers.

If you cannot do without synchronizing on the server side, you can choose between spaghetti code or a sync lib.