WrapCb will wrap all callbacks counting them and calling finalCb when all CB's were called

cbWrapper.js

var cbCounter = 0
function finalCb(){
	// Do something when all CBs are called
}

function wrapCb(cb, context){
	cbCounter++;
	return function(){  // context is optional, if you need to have the `this` changed for the CB
		cb && cb.call(context || this);  // so CB isn't mandatory
		cbCounter--;
		if(cbCounter === 0){
			finalCb();
		}
	}
}



/* test */

finalCb = console.log.bind(console, 'final cb'); // Overwriting the prototype from above

for(var i = 0; i < 5000; i++){
	setTimeout(wrapCb(console.log.bind(console, i)), 10);
}