photos.js

《JavaScript DOM编程艺术》一书中的配套源代码

function showPic(whichpic) {
  if (!document.getElementById("placeholder")) return true;
  var source = whichpic.getAttribute("href");
  var placeholder = document.getElementById("placeholder");
  placeholder.setAttribute("src",source);
  if (!document.getElementById("description")) return false;
  if (whichpic.getAttribute("title")) {
    var text = whichpic.getAttribute("title");
  } else {
    var text = "";
  }
  var description = document.getElementById("description");
  if (description.firstChild.nodeType == 3) {
    description.firstChild.nodeValue = text;
  }
  return false;
}

function preparePlaceholder() {
  if (!document.createElement) return false;
  if (!document.createTextNode) return false;
  if (!document.getElementById) return false;
  if (!document.getElementById("imagegallery")) return false;
  var placeholder = document.createElement("img");
  placeholder.setAttribute("id","placeholder");
  placeholder.setAttribute("src","images/placeholder.gif");
  placeholder.setAttribute("alt","my image gallery");
  var description = document.createElement("p");
  description.setAttribute("id","description");
  var desctext = document.createTextNode("Choose an image");
  description.appendChild(desctext);
  var gallery = document.getElementById("imagegallery");
  insertAfter(description,gallery);
  insertAfter(placeholder,description);
}

function prepareGallery() {
  if (!document.getElementsByTagName) return false;
  if (!document.getElementById) return false;
  if (!document.getElementById("imagegallery")) return false;
  var gallery = document.getElementById("imagegallery");
  var links = gallery.getElementsByTagName("a");
  for ( var i=0; i < links.length; i++) {
    links[i].onclick = function() {
      return showPic(this);
    }
  }
}

addLoadEvent(preparePlaceholder);
addLoadEvent(prepareGallery);