How to find out the section of Javascript that affects an HTML image slider element?

Question

I have an image slider, and I'm trying to figure out which part of the Javascript code affects the actual sliding behavior of the HTML element. The image slides from 1-2, 2-3, and then resets by sliding 3-2-1. I'm trying to set it up to where it loops and only slides 1-2, 2-3, 3-1. Any help is greatly appreciated.

THE HTML CODE:

<div id="slideShow">
  <!-- module slide_show start //-->

<div style="margin:2px 0px 10px 0px;">

  <div style="overflow: auto; height: 100%; margin: 0px auto;">
<div id="slideWrapper">
<div id="slideItems">
<span><a href="info.php?articles&articles_id=6"><img src="images/about-us.png" alt="" /></a></span>
<span><a href="info.php?articles&articles_id=1"><img src="images/services.png" alt="" /></a></span>
<span><a href="http://www.acehardware.com/acerewards/"><img src="images/ace-rewards.png" alt="" /></a></span>
</div>
</div>
          </div>
 <script type="text/javascript">
            window.addEvent('domready',function(){
                var slide_show = new noobSlide({
                mode: 'horizontal',items: [0,1,2],size: 960,
                box: $('slideItems'),
                interval: 10000,
                duration: 1000,autoPlay: true});
        });</script>
</div>
<!-- module slide_show end //--></div>

THE JAVASCRIPT CODE:

/*
Author:
    luistar15, <leo020588 [at] gmail.com>
License:
    MIT License

Class
    noobSlide (rev.19-06-08)

Arguments:
    Parameters - see Parameters below

Parameters:
    box: dom element | required
    items: dom collection | required
    size: int | item size (px) | default: 240
    mode: string | 'horizontal', 'vertical' | default: 'horizontal'
    addButtons:{
        previous: single dom element OR dom collection| default: null
        next:  single dom element OR dom collection | default: null
        play:  single dom element OR dom collection | default: null
        playback:  single dom element OR dom collection | default: null
        stop:  single dom element OR dom collection | default: null
    }
    button_event: string | event type | default: 'click'
    handles: dom collection | default: null
    handle_event: string | event type| default: 'click'
    fxOptions: object | Fx.Tween options | default: {duration:500,wait:false}
    interval: int | for periodical | default: 5000
    autoPlay: boolean | default: false
    onWalk: event | pass arguments: currentItem, currentHandle | default: null
    startItem: int | default: 0

Properties:
    box: dom element
    items: dom collection
    size: int
    mode: string
    buttons: object
    button_event: string
    handles: dom collection
    handle_event: string
    previousIndex: int
    nextIndex: int
    fx: Fx.Tween instance
    interval: int
    autoPlay: boolean
    onWalk: function

Methods:
    previous(manual): walk to previous item
        manual: bolean | default:false
    next(manual): walk to next item
        manual: bolean | default:false
    play (interval,direction,wait): auto walk items
        interval: int | required
        direction: string | "previous" or "next" | required
        wait: boolean | required
    stop(): stop auto walk
    walk(item,manual,noFx): walk to item
        item: int | required
        manual: bolean | default:false
        noFx: boolean | default:false
    addHandleButtons(handles):
        handles: dom collection | required
    addActionButtons(action,buttons):
        action: string | "previous", "next", "play", "playback", "stop" | required
        buttons: dom collection | required

Requires:
    mootools 1.2 core
*/
var noobSlide = new Class({

    initialize: function(params){
        this.items = params.items;
        this.mode = params.mode || 'horizontal';
        this.modes = {horizontal:['left','width'], vertical:['top','height']};
        this.size = params.size || 240;
        this.box = params.box.setStyle(this.modes[this.mode][1],(this.size*this.items.length)+'px');
        this.button_event = params.button_event || 'click';
        this.handle_event = params.handle_event || 'click';
        this.onWalk = params.onWalk || null;
        this.currentIndex = null;
        this.previousIndex = null;
        this.nextIndex = null;
        this.interval = params.interval || 5000;
        this.duration = params.duration || 500;
        this.autoPlay = params.autoPlay || false;
        this._play = null;
        this.handles = params.handles || null;
        if(this.handles){
            this.addHandleButtons(this.handles);
        }
        this.buttons = {
            previous: [],
            next: [],
            play: [],
            playback: [],
            stop: []
        };
        if(params.addButtons){
            for(var action in params.addButtons){
                this.addActionButtons(action, $type(params.addButtons[action])=='array' ? params.addButtons[action] : [params.addButtons[action]]);
            }
        }
        this.fx = new Fx.Tween(this.box,$extend((params.fxOptions||{duration:this.duration,wait:false}),{property:this.modes[this.mode][0]}));
        this.walk((params.startItem||0),true,true);
    },

    addHandleButtons: function(handles){
        for(var i=0;i<handles.length;i++){
            handles[i].addEvent(this.handle_event,this.walk.bind(this,[i,true]));
        }
    },

    addActionButtons: function(action,buttons){
        for(var i=0; i<buttons.length; i++){
            switch(action){
                case 'previous': buttons[i].addEvent(this.button_event,this.previous.bind(this,[true])); break;
                case 'next': buttons[i].addEvent(this.button_event,this.next.bind(this,[true])); break;
                case 'play': buttons[i].addEvent(this.button_event,this.play.bind(this,[this.interval,'next',false])); break;
                case 'playback': buttons[i].addEvent(this.button_event,this.play.bind(this,[this.interval,'previous',false])); break;
                case 'stop': buttons[i].addEvent(this.button_event,this.stop.bind(this)); break;
            }
            this.buttons[action].push(buttons[i]);
        }
    },

    previous: function(manual){
        this.walk((this.currentIndex>0 ? this.currentIndex-1 : this.items.length-1),manual);
    },

    next: function(manual){
        this.walk((this.currentIndex<this.items.length-1 ? this.currentIndex+1 : 0),manual);
    },

    play: function(interval,direction,wait){
        this.stop();
        if(!wait){
            this[direction](false);
        }
        this._play = this[direction].periodical(interval,this,[false]);
    },

    stop: function(){
        $clear(this._play);
    },

    walk: function(item,manual,noFx){
        if(item!=this.currentIndex){
            this.currentIndex=item;
            this.previousIndex = this.currentIndex + (this.currentIndex>0 ? -1 : this.items.length-1);
            this.nextIndex = this.currentIndex + (this.currentIndex<this.items.length-1 ? 1 : 1-this.items.length);
            if(manual){
                this.stop();
            }
            if(noFx){
                this.fx.cancel().set((this.size*-this.currentIndex)+'px');
            }else{
                this.fx.start(this.size*-this.currentIndex);
            }
            if(manual && this.autoPlay){
                this.play(this.interval,'next',true);
            }
            if(this.onWalk){
                this.onWalk((this.items[this.currentIndex] || null), (this.handles && this.handles[this.currentIndex] ? this.handles[this.currentIndex] : null));
            }
        }
    }

});

Answer 1

You need only look at the names of the JavaScript methods.

next()
 -> this.walk(...)
     -> this.fx.start(...)

The this.fx property comes from:

this.fx = new Fx.Tween(...)

In the initialize() method. Reading up on the Prototype JavaScript library would be a good idea.