Javascript image rotator viewer

posted by Alex Grande

See a demo at http://www.alexgrande.com
It is the images on the top right.
I wrote this in Object Oriented format so you can use it again again on page.
Javascript:

var ImageGallery = new Function();

ImageGallery.prototype = {
 initialize: function(mainImage, listWrapper){
  // large image that is shown
  this.mainImage = document.getElementById(mainImage);
  // a list of all the anchors for the thumbnails. Must be a tags for graceful degradation
  this.thumbnails = document.getElementById(listWrapper).getElementsByTagName("a");
  // 0 image is shown already so the first one we want to switch to is the next image or 1
  this.i = 1;
  // this is a work around to allow calling this within nested functions
  var Scope = this;
  // Here starts the rotating of the image by first focusing the thumbnail, then switch the primary image
  this.start = setInterval(function(){
   Scope.focusCall();
  // Here we choose 5 seconds in between each image change. You may want to change this.
  }, 5000);
  // This lets the browser know to do something if one of the thumbnails is clicked
  this.clickEvent();
 },
 
 // This stops the rotation of the thumbnails. We do that if the user clicks one of them
 stop: function(){
  if (this.start) 
   clearInterval(this.start);
 },
 
 // When an thumbnail loses focus we must use this css class now
 resetBorderColor: function(reset){
  reset.getElementsByTagName("img")[0].className="thumbnailDefault";
 },
 
 // When the thumbnail gains focus we most give it the corresponding styles
 focusBorderColor: function(focused){
  focused.getElementsByTagName("img")[0].className="thumbnailFocus";
 },
 
 
 // Here we grab the href of the a tags and make their path be the path of the current image
 imageRotator: function(){
  this.mainImage.src = this.thumbnails[this.i].href;
  this.previousImage = this.thumbnails[this.i];
  this.i++;
  // This closes the loop for the rotation
  if (this.i == this.thumbnails.length) 
   this.i = 0;
 },
 
 // We focus the thumbnail
 focusCall: function(){
  // reset the last image that was shown
  if (typeof this.previousImage != 'undefined') 
   this.resetBorderColor(this.previousImage);
  // Remember the newer one
  this.currentImage = this.thumbnails[this.i];
  // Give the newer image some focus
  this.focusBorderColor(this.currentImage);
  var Scope = this;
  // Les that have image rotate to the new one 300 miliseconds after the thumbnails get the css focus
  window.setTimeout(function(){
   Scope.imageRotator()
  // You may want to change this number 
  }, 300);
  
 },
 
 // This is what happens when you click the thumbnails
 clickEvent: function(){
  var Scope = this;
  for (k = 0; k < this.thumbnails.length; k++) {
   this.thumbnails[k].onclick = function(){
    if (typeof Scope.previousImage != 'undefined') 
     Scope.resetBorderColor(Scope.previousImage);
    Scope.focusBorderColor(this);
    // Stop the rotation 
    Scope.stop();
    // This is where the switching happens for the click
    Scope.mainImage.src = this.href;
    Scope.previousImage = this;
    // Make sure to not allow default behavior of the a tag
    return false;
   }
  }
 }
 
}

This is to load it on the window object and create an instance of the viewer

var imageGallery1 = new ImageGallery();

// Not sure where I got this.. I didn't write this but it allows you to load multiple functions on the window.onload.
function addLoadEvent(func) {
 var oldonload = window.onload;
 if (typeof window.onload != "function") {
  window.onload = func;
 } else {
  window.onload = function() {
   oldonload();
   func();
  }
 }
}

var onLoad = function() {
 imageGallery1.initialize("index_largepic_display", "index_thumbnail_display");
}
 

addLoadEvent(onLoad);

For the version on my homepage alexgrande.com here is the CSS and HTML. The CSS is up to you but I suggest following a similar mode with the HTML

HTML:

<div id="gallery">   
     <ul id="index_thumbnail_display">
        <li> 
   <a href="images/index/fernlarge.jpg" >
  <img class="thumbnailDefault" src="images/index/fernthumb.jpg" alt="A picture of a fern just as it is unraveling in front of a log." />
   </a> 
 </li>

        <li> 
   <a id="partythumb" href="images/index/partylarge.jpg" >
      <img class="thumbnailDefault" src="images/index/partythumb.jpg" alt="Downtown Seattle at night." />
   </a>
 </li>

        <li> 
   <a id="alexthumb" href="images/index/alexlarge.jpg" >
      <img class="thumbnailDefault" src="images/index/alexthumb.jpg" alt="I'm on a laptop at night in a field on using the internet via hacking a telephone box...legally." />
   </a> 
 </li>
        <li> 
   <a href="images/index/trucks.jpg" >
     <img class="thumbnailDefault" alt="Trucks lined up in Sodo in Seattle at night." src="images/index/trucksthumb.jpg" />
   </a> 
        </li>
      </ul>
      <img id="index_largepic_display" src="images/index/fernlarge.jpg" alt="A picture of a fern just as it is unraveling in front of a log." /> 
</div>

CSS:

div#gallery {
 position:relative; 
 float: left;
 overflow: hidden;
 width: 65%;
}

img#index_image_display {
 border:1px black solid;
 margin-bottom:20px;
}

ul#index_thumbnail_display {
 list-style-type:none;
 position:absolute; 
 top: 0;
 left: 0;
 margin-top: 15px;
}

ul#index_thumbnail_display li a {
 padding:10px;
}

.thumbnailDefault {border: 1px solid gray !important;}

.thumbnailFocus {border: 1px solid red !important;}