gistfile1.js

// fire a callback after enough keys have been passed to a generated function
var dependencySet = function(conditionKeys, callback){
  // convert a list of keys to trackable hash
  var conditionSet = {}    
  for(var x=0;x<conditionKeys.length;x++){
    conditionSet[conditionKeys[x]] = false;
  }
  
  // return a function that will wait till it's 
  // been called with all keys and then fire the callback
  return function(val){
    if(conditionSet[val] == null){ console.error("Bad argument",val); return; }
    conditionSet[val]=true
    var allTrue = true;
    for(var x in conditionSet){
      if(conditionSet[x]==false){
        allTrue = false;
      }
    }
    if(allTrue){
      callback();
    }
  }
}

// usage
var t = dependencySet(['a','b'],function(){ console.log("asd"); });
t("a");
t("b");