<p>
 The <abbr title="World Wide Web Consortium">W3C</abbr> defines
 the <abbr title="Document Object Model">DOM</abbr> as:
 </p>
 <blockquote cite="http://www.w3.org/DOM/">
 <p>
 A platform- and language-neutral interface that will allow programs
 and scripts to dynamically access and update the
 content, structure and style of documents.
 </p>
 </blockquote>
 <p>
 It is an <abbr title="Application Programming Interface">API</abbr>
 that can be used to navigate <abbr title="HyperText Markup Language">HTML</abbr>
 and <abbr title="eXtensible Markup Language">XML</abbr> documents.
 </p>

<dl>
 <dt>缩略语标题/abbr.lastChild.nodeValue</dt>
 <dd>缩略语定义描述/abbr.getAttribute</dd>
 ......
</dl>

function displayAbbreviations() {
 //注释1：注意这里没有对DOM方法做兼容性检查
 var abbreviations = document.getElementsByTagName("abbr");
 var defs = new Array();//注释2：用数组的键值对来保存abbr的title属性和文本
 //loop through the abbr list
 for (var i=0; i<abbreviations.length; i++) {
 var current_abbr = abbrevaitons[i];
 //注释3：if (current_abbr.childNodes.length < 1) continue;
 var defination = current_abbr.getAttributes("title");
 var key = current_abbr.lastChild.nodeValue;
 defs[key] = defination;
 }
 var dlist = document.createElement("dl");
 //loop through the defs
 for (key in defs) {
 var defination = defs[key];
 var dtitle = document.createElement("dt");
 var dtitle_text = document.createTextNode(key);
 dtitle.appendChild(dtitle_text);
 var ddesc = document.createElement("dd");
 var ddesc_text = document.createTextNode(defination);
 ddesc.appendChild(ddesc_text);
 dlist.appendChild(dtitle);
 dlist.appendChild(ddesc);
 }
 //注释4：if (dlist.childNodes.length < 1) return false;
 var header = document.createElement("h2");
 var header_text = document.createElement("Abbreviations");
 header.appendChild(header_text);
 //注释5：下面两行用到了HTML-DOM属性：document.body，也可以用DOM core的 document.getElementsByTagName("body")[0]方法;
 document.body.appendChild(header);
 document.body.appendChild(dlist);
}

function displayCitations() {
　　　　//兼容性检查
 if (!document.getElementsByTagName || !document.createElement
 || !document.createTextNode) return false;
 //获取所有的blockquote元素
 var quotes = document.getElementsByTagName("blockquote");
 //1 遍历blockquote元素
 for (var i=0; i<quotes.length; i++) {
 // 检查是否存在cite属性
 if (!quotes[i].getAttribute("cite")) continue;
 // 2 提取cite属性的值
 var url = quotes[i].getAttribute("cite");
 // 获取blockquote包含的所有元素节点，注意是元素节点，这样就把文本节点排除掉了
 var quoteChildren = quotes[i].getElementsByTagName("*");
 // 判断元素是否为空
 if (quoteChildren.length < 1) continue;
 var elem = quoteChildren[quoteChildren.length - 1];//获取最后一个元素节点
 var link = document.createElement("a");//3 创建链接节点
 var link_text = document.createTextNode("source");
 link.appendChild(link_text);
 link.setAttribute("href", url);//4 给链接节点的href属性赋值
 var superscript = document.createElement("sup");
 superscript.appendChild(link);
 elem.appendChild(superscript);//5 追加节点到<blockquote>包含节点的末尾
 }
}

<ul id="navigation">
 <li><a href="index.html" accesskey="1">Home</a></li>
 <li><a href="search.html" accesskey="4">Search</a></li>
 <li><a href="contact.html" accesskey="0">Contact</a></li>
 </ul>

function displayAccesskeys() {
 if (!document.getElementsByTagName || !document.createElement || !document.createTextNode) return false;
// get all the links in the document
 var links = document.getElementsByTagName("a");
// create an array to store the accesskeys
 var akeys = new Array();
// loop through the links
 for (var i=0; i<links.length; i++) {
 var current_link = links[i];
// if there is no accesskey attribute, continue the loop
 if (current_link.getAttribute("accesskey") == null) continue;
// get the value of the accesskey
 var key = current_link.getAttribute("accesskey");
// get the value of the link text
 var text = current_link.lastChild.nodeValue;
// add them to the array
 akeys[key] = text;
 }
// create the list
 var list = document.createElement("ul");
// loop through the accesskeys
 for (key in akeys) {
 var text = akeys[key];
// create the string to put in the list item
 var str = key + " : "+text;
// create the list item
 var item = document.createElement("li");
 var item_text = document.createTextNode(str);
 item.appendChild(item_text);
// add the list item to the list
 list.appendChild(item);
 }
// create a headline
 var header = document.createElement("h3");
 var header_text = document.createTextNode("Accesskeys");
 header.appendChild(header_text);
// add the headline to the body
 document.body.appendChild(header);
// add the list to the body
 document.body.appendChild(list);
}
addLoadEvent(displayAccesskeys);