var A = function() {}
var B = function() {}

// factory
var Type = function(name) {
  if(name === "a") {
    return new A();
  }
  else {
    return new B();
  }
}

// example of using the above factory

// dummy data to show example
var myArray = ["a", "a", "b", "c", "b", "a"];

// loop through array
for(var i = 0; i < myArray.length; i++) {
  // will create a new A or B depending on what the factory decides
  new Type(myArray[i]);
}