function extend(subClass, baseClass) {
   function inheritance() {}
   inheritance.prototype = baseClass.prototype;

   subClass.prototype = new inheritance();
   subClass.prototype.constructor = subClass;
   subClass.baseConstructor = baseClass;
   subClass.superClass = baseClass.prototype;
}

function randomArrayIndex(array) {
    return Math.floor(Math.random() * array.length);
}