The Timer Class, For Object-oriented Timeouts

The problems with the setTimeout and setInterval functions provided in Javascript are twofold. First, you can't call a local object method without losing your scope, and second, you can't pass objects to the function, since the function call is implemented as a string.

The Timer class solves these difficulties by employing a static array to store the parent object and function arguments until the function is called.

This class is provided as-is and pro bono, so go ahead and muck with it if you see things that could be done better.

Thanks to WA for giving me the idea for this (albeit indirectly)!

Updated 4/18/2003: Footprint decreased, minor code improvements.
Updated 5/3/2003: Minor comment clarification; no code changes.
Updated 5/10/2003: Minor code improvements.
// The constructor should be called with
// the parent object (optional, defaults to window).

function Timer(){
this.obj = (arguments.length)?arguments[0]:window;
return this;
}

// The set functions should be called with:
// - The name of the object method (as a string) (required)
// - The millisecond delay (required)
// - Any number of extra arguments, which will all be
// passed to the method when it is evaluated.

Timer.prototype.setInterval = function(func, msec){
var i = Timer.getNew();
var t = Timer.buildCall(this.obj, i, arguments);
Timer.set[i].timer = window.setInterval(t,msec);
return i;
}
Timer.prototype.setTimeout = function(func, msec){
var i = Timer.getNew();
Timer.buildCall(this.obj, i, arguments);
Timer.set[i].timer = window.setTimeout("Timer.callOnce("+i+");",msec);
return i;
}

// The clear functions should be called with
// the return value from the equivalent set function.

Timer.prototype.clearInterval = function(i){
if(!Timer.set[i]) return;
window.clearInterval(Timer.set[i].timer);
Timer.set[i] = null;
}
Timer.prototype.clearTimeout = function(i){
if(!Timer.set[i]) return;
window.clearTimeout(Timer.set[i].timer);
Timer.set[i] = null;
}

// Private data

Timer.set = new Array();
Timer.buildCall = function(obj, i, args){
var t = "";
Timer.set[i] = new Array();
if(obj != window){
Timer.set[i].obj = obj;
t = "Timer.set["+i+"].obj.";
}
t += args[0]+"(";
if(args.length > 2){
Timer.set[i][0] = args[2];
t += "Timer.set["+i+"][0]";
for(var j=1; (j+2)<args.length; j++){
Timer.set[i][j] = args[j+2];
t += ", Timer.set["+i+"]["+j+"]";
}}
t += ");";
Timer.set[i].call = t;
return t;
}
Timer.callOnce = function(i){
if(!Timer.set[i]) return;
eval(Timer.set[i].call);
Timer.set[i] = null;
}
Timer.getNew = function(){
var i = 0;
while(Timer.set[i]) i++;
return i;
}
Here's an example of the code in action:
function Ticker(){
this.count = 0;
this.timer = new Timer(this);
}
Ticker.prototype.tick = function(d){
this.count+=d;
window.status = ""+this.count;
this.timer.setTimeout("tick", 1000, d);
}

window.onload = function(){
var ticker = new Ticker();
ticker.tick(1);
}