Message Center: Image/Text Rotator

This here is a script that I've used in a few different sites, namely art/graphic/image-related sites. It's designed to rotate through banner ads, images, text, or anything else. I've tried to make it as easy to use as possible, so let me know what you think. Efficiency and functionality improvement suggestions are always welcome. =)

Documentation is available (http://www.skyzyx.com/scripts/messagecenter.php), and you can download the script with a demo page at the bottom of this post.

One thing that I built-in is a user's ability to stop the content from rotating (assuming the web designer makes the function available on his/her website), which helps to conform to the Web Content Accessibility Guidelines about "no or uncontrollable screen flickering".


/*************************************
MESSAGE CENTER 5.1
(c) 2002-03, Ryan Parman
http://www.skyzyx.com
Distributed according to SkyGPL 2.1,
http://www.skyzyx.com/license/
*************************************/


/*************************************
Updated September 2, 2003

v5.1 - Added Next() and Previous(). Also added "aliases" for many
functions to help a coder's logical naming style. Changed Resume()
into an alias for Start(). Streamlined and optimized code for efficiency.

v5.0 - Completely rewrote this script from the ground-up to be object-
oriented in nature. Implemented Algorithm's OO Timeouts. Functions
include addMessage(), start(), pause(), resume(), and clear().
*************************************/
function messageCenter(zSpanID, zDelayMS)
{
// INITIALIZATION
var spanid=zSpanID;
var delay=(zDelayMS) ? zDelayMS:4000;
var messageArray=new Array();
var count=0;
var tOut=new Timer(this);
var tOutRef, tOutRev;
var prevAcct=0;
var nextAcct=0;

// ADD A MESSAGE
// The parameter must be an HTML or text string.
this.addMessage=function(zMessage) {
messageArray[messageArray.length]=zMessage;
}

// START MESSAGE CENTER
// Usually this will be called on the onload of the BODY tag.
this.start=function() {
if (document.getElementById) {
document.getElementById(spanid).innerHTML=messageArray[count];
count++;
if (count > (messageArray.length-1)) count=0;
}
tOut.clearTimeout(tOutRev);
tOutRef=tOut.setTimeout("start", delay);
nextAcct=0;
prevAcct=0;
}

// start() aliases:
this.resume=function() { this.start(); }

// PAUSE FUNCTION
// This will pause the Message Center. Optionally, passing a String parameter will display that string while paused.
this.pause=function(stopMessage) {
this.stopMsg=(stopMessage) ? stopMessage:null;
tOut.clearTimeout(tOutRef);
if (this.stopMsg) document.getElementById(spanid).innerHTML=this.stopMsg;
}

// pause() aliases:
this.stop=function(stopMessage_stop) { this.pause(stopMessage_stop); }

// CLEAR FUNCTION
// This will stop the Message Center, and clear the element's contents.
this.clear=function() {
tOut.clearTimeout(tOutRef);
document.getElementById(spanid).innerHTML=''
count=0;
nextAcct=0;
prevAcct=0;
}

// clear() aliases:
this.end=function() { this.clear(); }
this.kill=function() { this.clear(); }
this.NoDisassembleNumberFive=function() { this.clear(); }

// NEXT FUNCTION
// This will skip to the next message, and pause the Message Center.
this.next=function() {
if (nextAcct == 0) { nextAcct=1; prevAcct=1 }
else if (nextAcct != 0) count++;
if (count > (messageArray.length-1)) count=0;
if (count < 0) count=messageArray.length-1;
tOut.clearTimeout(tOutRef);
document.getElementById(spanid).innerHTML=messageArray[count];
}

// next() aliases:
this.forward=function() { this.next(); }
this.fwd=function() { this.next(); }

// PREVIOUS FUNCTION
// This will skip to the previous message, and pause the Message Center.
this.previous=function() {
if (prevAcct == 0) { prevAcct=1; count-=2; nextAcct=1; }
else if (prevAcct != 0) count--;
if (count > (messageArray.length-1)) count=0;
if (count < 0) count=messageArray.length-1;
tOut.clearTimeout(tOutRef);
document.getElementById(spanid).innerHTML=messageArray[count];
}

// previous() aliases:
this.prev=function() { this.previous(); }
this.back=function() { this.previous(); }
}


/*************************************
Utilizes Algorithm's Timer Class for Object-Oriented timeouts
http://www.undefined.net
*************************************/
function Timer() {
this.obj = (arguments.length)?arguments[0]:window;
return this;
}

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;
}

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;
}

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;
}