Register namespace, and class

            Type.registerNamespace("Demo");

            Demo.Person = function(firstName, lastName, emailAddress) {
            this._firstName = firstName;
            this._lastName = lastName;
            this._emailAddress = emailAddress;
            }

            Demo.Person.prototype = {

            getFirstName: function() {
            return this._firstName;
            },

            getLastName: function() {
            return this._lastName;
            },

            getName: function() {
            return this._firstName + ' ' + this._lastName;
            },

            dispose: function() {
            alert('bye ' + this.getName());
            }
            }
            Demo.Person.registerClass('Demo.Person', null, Sys.IDisposable);

            // Notify ScriptManager that this is the end of the script.
            if (typeof(Sys) !== 'undefined') Sys.Application.notifyScriptLoaded();