返回文档的链接数

<img src="/examples/planets.gif" width="145" height="126" alt="Planets" usemap="#planetmap">

<map name="planetmap">

<area shape="rect" coords="0,0,82,126" href="/examples/sun.htm" alt="Sun">

<area shape="circle" coords="90,58,3" href="/examples/mercur.htm" alt="Mercury">

<area shape="circle" coords="124,58,8" href="venus.htm" alt="Venus">

</map>

<p><a href="/js/">JavaScript 教程</a></p>

<p>链接/地址数目:

  <script>

    document.write(document.links.length);

  </script>

</p>