Getters and Setters in Javascript

function addGetter(element, property, method) {
  if(typeof(element.prototype.__defineGetter__) != "undefined") {
    element.prototype.__defineGetter__(property, method);
  } else {
    try {
      eval("element[prototype][property] getter = method");
    } catch(e) {
      debug("Failed to add getter for " + property + " to " + element);
    }
  }
}

function addSetter(element, property, method) {
  if(typeof(element.prototype.__defineSetter__) != "undefined") {
    element.prototype.__defineSetter__(property, method);
  } else {
    try {
      eval("element.prototype[property] setter = method");
    } catch(e) {
      if(typeof(element.watch) != "undefined") {
        var wrapper = function(value) {
          arguments.callee.watchedElement.unwatch(arguments.callee.watchedProperty);
          arguments.callee.setter(value);
          arguments.callee.watchedElement.watch
            (arguments.callee.watchedProperty, arguments.callee);
          return arguments.callee.watchedElement[arguments.callee.watchedProperty];
        }
        wrapper.setter = method;
        wrapper.watchedProperty = property;
        wrapper.watchedElement = element;
        element.watch(property, wrapper);
      } else {
        debug("Failed to add setter for " + property + " to " + element);
      }
    }
  }
}

TestObject = function() {}
TestObject.prototype = new Object;
var getterMethod = function() { return this.randomVar ? this.randomVar : 5 };
var setterMethod = function(val) { this.randomVar = val * 100 * Math.random() };
addGetter(TestObject, "dynamicVar", getterMethod);
addSetter(TestObject, "dynamicVar", setterMethod);
var testObject = new TestObject();
debug("Before Assignment: " + testObject.dynamicVar);
testObject.dynamicVar = 20;
debug("After Assignment: " + testObject.dynamicVar);