Async example

test.js

function doSomethingOnceAllAreDone(){
    console.log("Everything is done.");
}
function Item(delay){
    this.delay = delay;
}
Item.prototype.someAsyncCall = function(callback){
    setTimeout(function(){
        console.log("Item is done.");
        if(typeof callback === "function") callback();
    }, this.delay);
};
var items = [];
items.push(new Item(1000));
items.push(new Item(200));
items.push(new Item(500));


var async = require("async");

var asyncTasks = [];

items.forEach(function(item){


    asyncTasks.push(function(callback){

        item.someAsyncCall(function(){

            callback();
        });
    });
});


asyncTasks.push(function(callback){

    setTimeout(function(){
        console.log("Additional item is done.");
        callback();
    }, 3000);
});


async.waterfall(asyncTasks, function(){
    // All tasks are done now
    doSomethingOnceAllAreDone();
});