var Site = {
  footerStatus:"showed",
  showFooter = function() { // showFooter = function(var1,var2,...)
    $('#footer').show();
    this. footerStatus = "show";
  },
  hideFooter = function(){
    $('#footer').hide();
    this. footerStatus = "hide";
  }
  // you can use .toggle() as well.
}

var Animal = Class.create();
Animal.prototype = {
  initialize: function(){
    this.alive = true;
    this.full = false;
  },
  eat: function(food){
    if(food == "sticky-rice"){
      this.full = true;
      alert(this.full);
      return this.full;
    }
    return false;
  }
}
var myPet = new Animal();
myPet.eat("pizza");
myPet.eat("sticky-rice");  // alert "true"

Object.extend(Animal.prototype, {
    dieNow: function() {
      this.alive = false;
      alert(this.alive);
    }
  }
);
myPet.dieNow(); // alert "false"

Element.addMethods({
  say: function(element, word){
    if(!word)
      alert(element.innerHTML);
    else
      alert(word);
  }
});
$('footer').say();
$('footer').say("hello");