看看这个是怎么回事？？

Question

<script language="Javascript">
   function ChangePic(strnname)
   { 
 eval("document.images."+strnname).src="http://community.csdn.net/images/jspd_wdzx_sqgg_ad.gif";
   }   
</script><Span onclick="ChangePic('gold_1');" Style="cursor: hand"><img src="http://images.sohu.com/cs/sms/olympic/19652_040811.gif" width="140" height="30" ID="gold_1"></Span>

Answer 1

function ChangePic(strnname)
   { 
cmdstr="document.images." + strnname + ".src='images/gold_1_1.gif'";
eval(cmdstr);
   }

Answer 2

document.all(strnname).src="images/gold_1_1.gif"