JavaScript is a prototype-based OO language. Search on Google for the
"Self" programming language for more info on this concept since it is
the pioneer in this type of OO.
Brian Feliciano wrote:
is there a difference between:
var ObjectName = Class.create();
ObjectName.prototype = {
initialize: function () {},
doThis: function () {}
}
var obj = new ObjectName();
obj.doThis();
In this case you are creating a prototype object (located at
ObjectName.prototype) and defining a constructor function which will
spawn a new object from that prototype object, executing that
constructor function to create your new object then executing a method
on that new object. You can think of this as somewhat like doing the
following (it is a bit different but I'm trying to keep just the core
concepts here):
ObjectName.prototype = {
initialize: function () {},
doThis: function () {}
}
var obj = new Object();
obj.prototype = ObjectName.prototype;
obj.initialize();
obj.doThis();
What Prototype is trying to do here is trying to simulate class-based OO
on top of the built-in prototype-based OO. The idea is to treat the
object "ObjectName" as the class (and methods defined on this object
would be considered class methods). Instance methods are defined on
"ObjectName.prototype". "initialize" is your constructor for creating
new instances of your class. The goals is to make JavaScript more
comfortable to developers who are used to class-based OO that most OO
languages implement (Ruby, C#, Java, etc.)
var ObjectName = {
initialize: function () {},
doThis: function () {}
}
ObjectName.doThis();
This on the other hand is just using normal prototype-based OO. Here you
are creating an object literal (the stuff inside the {}) with your
methods defined and assigning that object literal to the identifier
"ObjectName". You are this using that object as a normal instance
without worrying about defining abstract concepts like classes.
It is important to note that your "initialize" method is not
automatically executed for you. That is something that prototype does
for you when you execute "Class.create()" (it defines a constructor
function which will execute "initialize" on the new instance being
created). No constructor is run when using an object literal. Only if
you define a constructor function and create new instances from the
constructor function's prototype object is a constructor executed.
Eric
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