javascript按一个标签值检索里一个标签值

Question

if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.open("GET","note.xml",false);
xmlhttp.send();
xmlDoc=xmlhttp.responseXML;

//var a=xmlDoc.getElementsByTagName("L1")[0].childNodes[0].nodeValue;
//document.write(a);
var str=4-1/2;
var x=xmlDoc.getElementsByTagName("item");
for(var i=0:i<x.length:i++)
{
if (str==x[i].getElementsByTagName("code")[0].childNodes[0].nodeValue)
{
var y=x[i].getElementsByTagName("L4")[0].childNodes[0].nodeValue;
}
}
document.write(y);

不显示y值

Answer 1

y是否解析到正确的html元素