function newImage(imgSrc)  {

 var imgName = new Image();
 imgName.src = imgSrc;

 return imgName;
}

function change( imgName, imgLocation )  {
  document[imgName].src = imgLocation;
}

var preloadFlag = false;


function loadImages(imgArr)  {
  if(document.images)  {
    for(var i = 0; i < imgArr.length; i++)  {
      slideImage = newImage(imgArr[i]);
    }

    preloadFlag = true;
  }
}


function changeImage(i, imgArr)  {
  var sliderIndex = document.getElementById("sliderIndex");
  sliderIndex.value = i;

  change("sliderImage", imgArr[i]);
}


function nextImage(imgArr)  {
  var sliderIndex = document.getElementById("sliderIndex");
  sliderIndex.value = parseInt(sliderIndex.value) + 1;

  if(imgArr[sliderIndex.value])  {  
    //ok, do nothing
  }
  else  {
    sliderIndex.value = sliderIndex.value - 1;
    e =  document.getElementById("sliderImage" + sliderIndex.value)
  }

  changeImage(sliderIndex.value, imgArr);
}


function prevImage(imgArr)  {
  var sliderIndex = document.getElementById("sliderIndex");
  sliderIndex.value = parseInt(sliderIndex.value) - 1;
  var e;

  if(imgArr[sliderIndex.value])  {  
    //ok, do nothing
  }
  else  {
    sliderIndex.value = 0;
    e =  document.getElementById("sliderImage" + sliderIndex.value)
  }

  changeImage(sliderIndex.value, imgArr);
}