1. Private/Public fields, Module, Revealing Module Learning & Development Team http://academy.telerik.com Telerik Software Academy

2. 1. Public/Private fields in JavaScript 2. Module pattern 3. Revealing module pattern 4. Revealing prototype pattern 5. Singleton pattern 2

3. Using the function scope

4.  Each variable is defined:  In the global scope (Public)  In a function scope (Private) 4 var global = 5; function myFunction() { var private = global; function innerFunction(){ var innerPrivate = private; }}

5. Live Demo

6. Hide members

7.  Pros:  “Modularize” code into re-useable objects  Variables/functions not in global namespace  Expose only public members  Cons:  Not easy to extend  Some complain about debugging 7

8. 8 var module = (function() { //private variables //private functions return { //public members someFunc: function() {…}, anotherFunc: function() {…} };}());  Structure:

9. 9 var controls = (function () { //hidden members //hidden members function formatResult(name, value) { //… } function formatResult(name, value) { //… } //visible members //visible members return { return { Calculator: function (name) { Calculator: function (name) { var result; var result; result = 0; result = 0; this.add = function (x) { //… }; this.add = function (x) { //… }; this.subtract = function (x) { //…}; this.subtract = function (x) { //…}; this.showResult = function () { //… }; this.showResult = function () { //… }; } }; };}()); var calc = new controls.Calculator('First'); calc.add(7);calc.showResult();  Example:

10. 10 var controls = (function () { //hidden members //hidden members function formatResult(name, value) { //… } function formatResult(name, value) { //… } //visible members //visible members return { return { Calculator: function (name) { Calculator: function (name) { var result; var result; result = 0; result = 0; this.add = function (x) { //… }; this.add = function (x) { //… }; this.subtract = function (x) { //…}; this.subtract = function (x) { //…}; this.showResult = function () { //… }; this.showResult = function () { //… }; } }; };}()); var calc = new controls.Calculator('First'); calc.add(7);calc.showResult();  Example: The visible members create closures with them

11. var controls = (function () { //hidden members //hidden members function formatResult(name, value) { //… } function formatResult(name, value) { //… } //visible members //visible members return { return { Calculator: function (name) { Calculator: function (name) { var result; var result; result = 0; result = 0; this.add = function (x) { //… }; this.add = function (x) { //… }; this.subtract = function (x) { //…}; this.subtract = function (x) { //…}; this.showResult = function () { //… }; this.showResult = function () { //… }; } }; };}()); var calc = new controls.Calculator('First'); calc.add(7);calc.showResult(); 11  Example: Visible function constructor

12.  Module pattern provides encapsulation of variables and functions  Provides a way to add visibility (public versus private) to members  Each object instance creates new copies of functions in memory 12

13. Live Demo

14. Reveal the most interesting members

15.  Pros:  “Modularize” code into re-useable objects  Variables/functions taken out of global namespace  Expose only visible members  "Cleaner" way to expose members  Easy to change members privacy  Cons:  Not easy to extend  Some complain about debugging  Hard to mock hidden objects for testing 15

16. 16 var module = (function() { //hidden variables //hidden functions return { //visible members //visible members someFunc: referenceToFunction anotherFunc: referenceToOtherFunction };}());  Structure:

17. 17 var controls = (function () { //hidden function //hidden function function formatResult(name, value) { // … } function formatResult(name, value) { // … } var Calculator = (function () { var Calculator = (function () { var Calculator = function (name) { // … }; var Calculator = function (name) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.showResult = function () { // …}; Calculator.prototype.showResult = function () { // …}; return Calculator; return Calculator; }()); }()); return { return { Calculator: Calculator Calculator: Calculator }; };}()); var calc = new controls.Calculator('First');  Example:

18. 18 var controls = (function () { //hidden function //hidden function function formatResult(name, value) { // … } function formatResult(name, value) { // … } var Calculator = (function () { var Calculator = (function () { var Calculator = function (name) { // … }; var Calculator = function (name) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.showResult = function () { // …}; Calculator.prototype.showResult = function () { // …}; return Calculator; return Calculator; }()); }()); return { return { Calculator: Calculator Calculator: Calculator }; };}()); var calc = new controls.Calculator('First');  Example: Create the function constructor hidden

19. 19 var controls = (function () { //hidden function //hidden function function formatResult(name, value) { // … } function formatResult(name, value) { // … } var Calculator = (function () { var Calculator = (function () { var Calculator = function (name) { // … }; var Calculator = function (name) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.add = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.subtract = function (x) { // … }; Calculator.prototype.showResult = function () { // …}; Calculator.prototype.showResult = function () { // …}; return Calculator; return Calculator; }()); }()); return { return { Calculator: Calculator Calculator: Calculator }; };}()); var calc = new controls.Calculator('First');  Example: Expose (reveal) only references to hidden member

20.  Module pattern provides encapsulation of variables and functions  Provides a way to add visibility (public versus private) to members  Extending objects can be difficult since no prototyping is used 20

21. Live Demo

22. Reveal the most interesting members (again)

23.  Pros:  “Modularize” code into re-useable objects  Variables/functions taken out of global namespace  Expose only public members  Functions are loaded into memory once  Extensible  Cons:  "this" can be tricky  Constructor is separated from prototype 23

24. 24 var Constructor = function () { //constructor defined here } Constructor.prototype = (function() { //hidden variables //hidden functions return { //exposed members //exposed members someFunc: pointerToSomeFunc anotherFunc: pointerToAnotherFunc };}());  Structure:

25. 25 var Calculator = function (name) { // … }; Calculator.prototype = (function () { var add, subtract, showResult, formatResult; var add, subtract, showResult, formatResult; add = function (x) { // … }; add = function (x) { // … }; subtract = function (x) { // … }; subtract = function (x) { // … }; showResult = function () { // … }; showResult = function () { // … }; formatResult = function (name, value) { // … }; formatResult = function (name, value) { // … }; return { return { add: add, add: add, subtract: subtract, subtract: subtract, showResult: showResult showResult: showResult }; };}()); var calc = new Calculator('First');  Example:

26.  Module pattern provides encapsulation of variables and functions  Provides a way to add visibility (exposed versus hidden) to members  Provides extension capabilities 26

27. Live Demo

28. One object to rule them all!

29. 29 var module = function() { var instance, getInstance; var instance, getInstance; return { return { getInstance: function(){ getInstance: function(){ if(!instance){ if(!instance){ instance = new Instance(); instance = new Instance(); } return instance; return instance; } }; };}();  Structure:

30. 30 var controls = function () { var Calculator, calculatorInstance; var Calculator, calculatorInstance; Calculator = (function () { Calculator = (function () { function Calculator() { //… } function Calculator() { //… } return Calculator; return Calculator; }()); }()); return { return { getCalculator: function () { getCalculator: function () { if (!calculatorInstance) { if (!calculatorInstance) { calculatorInstance = new Calculator(); calculatorInstance = new Calculator(); } return calculatorInstance; return calculatorInstance; } }; };}(); var calculator = controls.getCalculator();  Example:

31. Live Demo

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35. Create the Snake game using the Revealing module pattern. Design the game such that it has at least three modules.