Help with JavaScript Alterations

var files = new Array("photo1.jpg", "photo2.jpg", "photo3.jpg", "photo4.jpg", "photo5.jpg", "photo6.jpg", "photo7.jpg")
function showFileList()
{
	var uploadFiles = new Object();
	for (i=1;i<=ImageUploader1.UploadItems.Count;i++)
	{
		var uploadItem = ImageUploader1.UploadItems.Item(i);
		uploadFiles[uploadItem.fileName.split("\\").reverse()[0]]=1;
	}
	var fileList = document.getElementById("fileList");
	while (fileList.options.length>0)
	{
		fileList.options.remove(0);
	}
	for (i=0;i<files.length;i++)
	{
		var fileName = files[i];
		if (uploadFiles[fileName]==undefined)
		{
	    	var option = document.createElement("OPTION");
			fileList.options.add(option);
			option.innerText = fileName;
			option.value = fileName;
		}
	}
}
function uploadClick()
{
	if (document.getElementById("fileList").options.length>0)
	{
		alert("Please select all photos specified in your upload cart.");
	}
	else
	{
		ImageUploader1.Send();
	}
}

function extractFileName(path)
{
	var idx1;
	var idx2;
	var idx = -1;
	var fileName;
	idx1 = path.lastIndexOf("/");
	idx2 = path.lastIndexOf("\\");
	idx = (idx1 > idx2) ? idx1 : idx2;
	if (idx > -1)
	{
		return path.substring(idx + 1, idx.length);
	}
	else
	{
		return path;
	}
}

var files = new Array("photo1.jpg", "photo2.jpg", "photo3.jpg", "photo4.jpg")

function ImageUploader_BeforeUpload()
{
	var imageUploader = getImageUploader("ImageUploader1");
	var missedFiles = new Object();
	var extraFiles = new Object();
	var count = imageUploader.getUploadFileCount();	

	var extraCount = 0;
	for (i = 1; i <= count; i++)
	{
		var uploadFileName = extractFileName(imageUploader.getUploadFileName(i));
		var foundSimilar = false;
		for (j = 0; j < files.length; j++)
		{			
			var currentFileName = files[j];
			if (uploadFileName == currentFileName)
			{
				foundSimilar = true;
				break;
			}
		}
		if (!foundSimilar)
		{
			extraFiles[extraCount] = uploadFileName;
			extraCount++;
		}
	}
	var missedCount = 0;
	for (j = 0; j < files.length; j++)
	{
		var currentFileName = files[j];		
		var foundSimilar = false;
		for (i = 1; i <= count; i++)
		{			
			var uploadFileName = extractFileName(imageUploader.getUploadFileName(i));
			if (uploadFileName == currentFileName)
			{
				foundSimilar = true;
				break;
			}
		}
		if (!foundSimilar)
		{
			missedFiles[missedCount] = currentFileName;
			missedCount++;
		}
	}
	var message = "";
	if (extraCount > 0)	//	Some extra files have been added to the upload list.
	{
		message += "The following files are extra:\n";
		for (i = 0; i < extraCount; i++)
		{
			message += extraFiles[i] + "\n";
		}
	}
	if (missedCount > 0)	//	Not all of the files from the list have been added to the upload list.
	{
		message += "The following files are missed:\n";
		for (i = 0; i < missedCount; i++)
		{
			message += missedFiles[i] + "\n";
		}
	}
	if (message.length > 0)
	{
		alert(message);
		return false;	//	Deny upload.
	}
	else
	{
		return true;	//	Allow upload.
	}
}
…
iu.addEventListener("BeforeUpload", "ImageUploader_BeforeUpload");