var interval = 3; // delay between rotating images (in seconds)
var random_display = 1; // 0 = no, 1 = yes
interval *= 1000;

function generate(x, y) {
  var range = y - x + 1;
  return Math.floor(Math.random() * range) + x;
}

function getNextIndex() {
  if (random_display) {
    image_index = generate(0, number_of_image-1);
  }
  else {
    image_index = (image_index+1) % number_of_image;
  }
  return(image_index);
}

function generateInnerHtml() {
  var next_index = getNextIndex();
  var new_image  = image_list[image_index].image;
  var new_url    = image_list[image_index].url;
  return("<a href=\""+new_url+"\" target=\"_blank\"><img src=\""+new_image+"\" alt=\"\" /></a>");
}

function rotateImage(place) {
  $(place).innerHTML = generateInnerHtml();
  var recur_call = "rotateImage('"+place+"')";
  setTimeout(recur_call, interval);
}