Javascript object orientation

Javascript does not use classes.  Javascript uses prototype-based programming.

Already existing objects are expanded ("decorated"). 



// A function to reate a custom object
	function Book (authorName, title, ISBN, pubDate) {
  			this.author = authorName;
  			this.title = title;
  			this.ISBN = ISBN;
  			this.date = pubDate;
  			this.toString = BookToString;
  			this.setTitle = BookSetTitle;
  			}
 
 // setting methods 			
  	function BookToString() {
  		var s="";
  		s = this.author + " " + this.title + " " + this.ISBN  + " " +this.date;
  		return s;
  		}
  			
  	function BookSetTitle(title) {
  		this.title = title;
  		}
  	
  			
// instantiating an object:
  	var text = new Book ("Heilmnn", "JavaScript with DOM...", "123", new Date("January 1, 2000"));
  	
  
  
// expanding on the custom object (all future instatiated objects with have cost:
  		Book.prototype.cost = "five dollars"; 	// "" is the default value
  		
// decorating a current object (only this object will now have rating.
text.rating = "3 stars";

text.printRating = function() { alert(text.rating); };


/***********************************************************************/

// So,  here is a custom object:

var Animal = function() {};

// instantiate an instance:
var pet1 = new Animal();

// Add a property to Animal
Animal.prototype.species = "something";

// Add a method to Animal
Animal.prototype.setSpecies = function(p) { this.species = p; }

// Add a different method to Animal (notice the property is created here)
Animal.prototype.setName = function(p) {this.name = p; }


/***********************************************************************/

Animal.prototype.toString = function() {
  var s = "";
  s = this.name + " " + this.species;
  return s;
  }
  
var pet2 = new Animal();
pet2.setSpecies("dog");
pet2.setName("Ada");
alert("pet2: " + pet2.toString() );

// can decorate an object without decorating all
pet2.cuteness = "very cute";
alert("pet2.cuteness: " + pet2.cuteness);