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var arr_files = new Array();
arr_files[0]         = 'pics/pic1.gif';
arr_files[1]         = 'pics/pic2.gif';
arr_files[2]         = 'pics/pic3.gif';
arr_files[3]         = 'pics/pic4.gif';

var current_file = new Array();

function switchpic(index, imgname) {
  if (document.images) {
    document.images[imgname].src = arr[index].src;
  }
}

function nextpic(imgname) {
  if (current_file[imgname] > 0) {
     current_file[imgname]++;
  } else {
     current_file[imgname] = 1;
  }
  if (current_file[imgname] >= arr_files.length) {
     current_file[imgname] = 0;
  }
  switchpic(current_file[imgname], imgname);
}

function prevpic(imgname) {
  if (current_file[imgname] > 0) {
     current_file[imgname]--;
  } else {
     current_file[imgname] = arr_files.length-1;
  }
  switchpic(current_file[imgname], imgname);
}

arr = new Array()
for (var img in arr_files) {
  arr[img] = new Image();
  arr[img].src = arr_files[img];
}

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x = 0;
var arr_files = new Array();
do{
    arr_files[x]= "images/about_portrait"+(x+1)+".gif"
    x++;
  }while(x<=10)

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document.getElementById('bildnummer').innerHTML = zahl;