Question

my problem is that i try to write a callback method in node.js
for different mysql selects and updates. The update commands must wait
for the data from the select to work with it. but sometimes they cant,
cause the vars are “undefined”. maybe i need a callback function to make
that work. In the following example there is a jQuery animation to wait
for before the callback starts. But how can i solve that with an mysql
command:

function mySandwich(param1, param2, callback) {  
        alert('Started eating my sandwich.\n\nIt has: ' + param1 + ', ' + param2);  

        $('#sandwich').animate({  
            opacity: 0  
        }, 5000, function() {  
            // Animation complete. 
            if (callback && typeof(callback) === "function") {  
            callback();  
        }   
        });  

    }  

    mySandwich('ham', 'cheese', function() {   
        alert('Finished eating my sandwich.');  
    });  

I hope someone can explain me that.
Best regards

Answer 1

I would recommend looking at async.js it allows for things to run in series, or parallel, and pass information on to either a final callback function or to the next function.