Execute a function once all dependencies have run.

ReadyListener.js

var ReadyListener = function(itemLength, fn){
    this.itemLength = itemLength;
    this.haveItems = 0;
    this.fn = fn;
};

ReadyListener.prototype.add = function(name){
    console.log('	'+name+': Ready');
    this.haveItems++;
    this.haveAllCheck();
};

ReadyListener.prototype.haveAllCheck = function(){
    if(this.haveItems === this.itemLength){
        this.fn();
    }
};

// Usage
var rl = new ReadyListener(lengthToAimFor, function(){
    // To run once length has reached lengthToAimFor
});

// Do something with callback function
doSomething(function(){
    rl.add('Done Something');
});