Question about Javascript getElementsByTagName method

I set the onclick event handler of one button i开发者_如何学编程n one of my iframes to add content to the table of another iframe of the same window,I use

var w = parent.frames[1].getElementsByTagName("tr"); 

this function should return a HTMLcollection object which is an Array-like object,but it seems that firefox and chrome can not parse my code because it can not execute

alert("here") ;

I placed after the getelement instruction,does anyone have a idea what is wrong,I am new to Web programming...

The function is getElementsByTagName("tag"); with a 's'.

You need a document object

" iframe.contentDocument" Not Working in IE8 and FF(3.5 and below) any other steps to solve this?

var doc;
var iframeObject = parent.document.getElementById('iframeID'); // MUST have an ID
if (iframeObject.contentDocument) { // DOM
  doc = iframeObject.contentDocument;
} 
else if (iframeObject.contentWindow) { // IE win
  doc = iframeObject.contentWindow.document;
}
if (doc) {
  var rows = doc.getElementsByTagName("tr");
}
else {
  alert('Wonder what browser this is...'+navigator.userAgent);
}

assuming the same domain