Javascript Object Problems

[MrFish]

I'm trying to make an animated gif class for the new html canvas. I start out by loading a bunch of images to the class and calling the start() function. This function does a setInterval function to call a run() function every second. But I can't get the function run to call any variables inside the class. They will all come up "undefined" or "NaN"

function AnimatedGif(){	//Variables	this.frames = new Array();	this.frameDuration = 1000;	this.image = new Image();	this.frame = 0;	this.runInterval;		this.loadImage = function(url)	{		fl = this.frames.length;		img = new Image();		img.src=url;		this.frames[fl] = img;	}		this.start = function()	{		this.runInterval = setInterval(this.run, this.frameDuration)	}		this.stop = function()	{		this.clearInterval(this.runInterval);		}		this.run = function()	{		frame = this.frame; //This is undefined at first, then NaN		frames = this.frames;		frameLength = frames.length;		this.image = frames[frame];		this.frame++;		if(this.frame == frameLength)		{			this.frame = 0;		}	}}

I've tried putting this.run in double quotes but then it won't even run.

[thescientist]

you should try declaring your local variable with the var keyword. did you try it as "this.run()"?it's most likely a scope issue with this and what it references within the setinterval function. you coudl trying something like this:

this.start = function(){  var ref = this;  this.runInterval = setInterval(ref.run, ref.frameDuration);};

[justsomeguy]

In order to specify the scope that the function runs in, one easy way is to add a createDelegate method to functions with this code:

Function.prototype.createDelegate = function(obj, args){  var method = this;  return function() {	var callArgs = args || arguments;	return method.apply(obj || window, callArgs);  };}

Then use this:this.runInterval = setInterval(this.run.createDelegate(this), this.frameDuration)That will make sure that when the function executes, this is set to the same object, or it's running in the same scope.

[MrFish]

That did it justsomeguy. Thanks for your help!