Dynamically Auto-Linking instance variables to object functions in javascript / jquery?

Question

Hey all,

I'm trying to create a robust audio player in javascript (& jQuery). I know that there are other players out there, but I'd like to try creating my own (so please don't refer me to jquery plugins). This is essentially what I would like to do:

Main.js:

var player = new Player(AudioObj); // Audio object links to Audio class (not shown)
player.buttons.play = $('play');
player.buttons.pause = $('pause'); // Play and pause ID's link to HTML Document Element

Player.js:

Player = function(Audio) {
   this.Audio = Audio;
   this.buttons = {};
   for(var button in this.buttons) {
      button.live('click', this.button); // This is the line I Have NO idea about..
   }
} 

Player.prototype = {
   play : function() {
      // Do Something
   },
   pause : function() {
      // Do something
   }
}

So essentially, I would like the properties to be pre-linked to object functions when you initialize the Player, and to just have it work when I link it to an HTML element.

Thanks! Matt Mueller

Answer 1

I think this would be a more OO way to go. Setup two more functions inside Player. One function would register a UI element to a Player action and another to unregister the action. So rather than keeping an explicit button collection you can just lean on jQuery.live and jQuery.die. For example:

function registerAction(selector, action) {
    // you could have some logic to map the passed in action
    // to the actual function name
    $(selector).live('click', action/functionName);
}
function unRegisterAction(selector, [action]) {
    // you could have some logic to map the passed in action
    // to the actual function name
    $(selector).die('click', [action/functionName]);
}

Then, your main.js example from above would become:

var player = new Player(AudioObj); // Audio object links to Audio class (not shown)
player.registerAction('#play', play);
player.registerAction('#pause', pause); // Play and pause ID's link to HTML Document Element

And your Player constructor would become:

Player = function(Audio) {
    this.Audio = Audio;        
}

Or something like that.

Answer 2

This is not the perfect solution but I find it to be pretty elegant:

Player.js

Player.prototype = {

 init: function() {
  var Player = this;

  // Attach buttons to respected functions
  for(var button in this.buttons) {
   if(typeof Player[button] === "function")
    $(this.buttons[button]).bind('click', {Player : this}, Player[button]);
  }
 },

 play: function(e){
  var Player = e.data.Player;
  var Audio = Player.Audio;

  Audio.play();
 },

 pause: function(e){
  var Player = e.data.Player;
  var Audio = Player.Audio;

  Audio.pause();  
 }
}

Main.js

 var audio = new AudioCore("UpToYou.mp3");
 var player = new Player(audio);
  player.buttons.play = $('#play');
  player.buttons.pause = $('#pause');
 player.init();

This provides a nice way to link buttons to the function without passing in a huge array or providing a bunch of options. I would be VERY happy to have a solution that would NOT require you to call init().