var photos;
   var sliderControl;
   var loadedData = false;
   var loadedPage = false;
   function update() {
    var index = window.sliderControl.getValue();
    var photo = photos[index];
    document.getElementById('caption').innerHTML = photo[0];
    document.getElementById('image').src = photo[1];
   }
   function initPage() {
    sliderControl = new Slider(document.getElementById("slider"), document.getElementById("slider-input"));
    loadedPage = true;
    if (loadedData) {
     go();
    }
   }
   function jsonFlickrApi(data) {
    var photoSet = data.photoset.photo;
    photos = [];
    for (var i = 0; i < photoSet.length; i++) {
     var photoData = photoSet[i];
     var url = 'http://farm' + photoData.farm + '.static.flickr.com/'+ photoData.server + '/' + photoData.id + '_' + photoData.secret + '.jpg';
     var title = photoData.title;
     photos[i] = [title, url];
     new Image().src = url; // prefetch
    }
    loadedData = true;
    if (loadedPage) {
     go();
    }
   }
   function go() {
    sliderControl.setMaximum(photos.length - 1);
    sliderControl.onchange = update;
    sliderControl.setUnitIncrement(1);
    update();
   }