Javascript function prototyping?

Question

I am learning PHASER HTML5 game dev framework based on javascript, during which I came across this piece of code which I am not able to understand

var BunnyDefender = {};        

BunnyDefender.Boot = function(game) {};

BunnyDefender.Boot.prototype = {    


preload: function()
   {                                       
    //-----to load objects and units before we begin our game
    this.load.image('preloadbar', 'images/loader_bar.png');         
    this.load.image('titleimage', 'images/TitleImage.png');
   },

create: function() 
    {

    this.input.addPointer();
    this.stage.backgroundColor = '#171642';

    this.state.start('Preloader');     // launches preloader from Boot.js         
     }

};

Here from what I had learnt about javascript prototyping was that , to add any method to an object or constructor function we used the following syntax/example:

 function employee(name,jobtitle,born)
  {
     this.name=name;
     this.jobtitle=jobtitle;
     this.born=born;
  }

 var fred=new employee("Fred Flintstone","Caveman",1970);
 employee.prototype.salary=null;
 fred.salary=20000;

Please help !!!

There isn't really a question in there. What part of the example code do you have trouble with? — Bob Brown, Aug 24 '14 at 10:02
BunnyDefender.Boot = function(game) {}; BunnyDefender.Boot.prototype = { ...} — UnixNoob, Aug 24 '14 at 10:09
The following answer covers constructor functions and prototype. Hope it helps: http://stackoverflow.com/a/16063711/1641941 — HMR, Aug 24 '14 at 12:35

David Barker · Answer 1 · 2014-08-24T11:00:55.907

So from what I understand from the question, you are not clear on static methods / properties in javascript.

Static methods can be called any time without creating a new instance of the class. Static methods are merely related code that may do something such as configure a class or uphold a design pattern such as creating / returning a singleton instance of the class.

// Constructor
var BunnyDefender = {};

// Prototype declarations
BunnyDefender.prototype = { ... }

// Static method implementing a crude singleton
BunnyDefender.Boot = function() {
    // Check if the static property _instance exists
    // if it doesn't. Create it one time only, thus our
    // BunnyDefender singleton is born.
    if ( ! BunnyDefender._instance )
        BunnyDefender._instance = new BunnyDefender();

    // Return the already created instance of BunnyDefender
    return BunnyDefender._instance;
};

As Boot is a static method of the class BunnyDefender we can call it without creating a new instance of bunny defender.

var bunnyDefender = BunnyDefender.Boot();

You can read more about static properties / methods in javascript tutorials/documentation such as this article.

Javascript function prototyping?

1 Answers1